The Daily Grind: A day in the field

The days are long. Every day for 5 days a week I wake up at 5:30 AM, and that’s sleeping in! I quickly pull on my old dirt brown boy child sized cargo pants and whatever clean shirt I can find in the dark, stick my hair in a bun and head downstairs to the communal kitchen. Since I sleep in I’m usually late for breakfast, but so long as there is still coffee, heads don’t roll.

Back at again with the white vans!

Everyone got a zombie look in their eye save for that one morning person who cheerier than a seagull with a French fry. It takes us the rest of us non-morning people a solid 10 minutes for the caffeine from the coffee to sink into our bloodstream. By 5:50 AM the team piles into the 3 white vans before heading over to the lab to grab all our equipment we’ll need for the day. Apparently, white vans are considered undesirable for stealing, sorry Daniel.

Typically, when we arrive at the lab we are greeted with the sun rising over the beach. While it sucks to be awake so early, it is almost worth it to see the sun rising every day. Each person is responsible for obtaining their equipment which is dependent upon what job you must conduct. Based on a rotating bi-weekly schedule each person will switch from being an excavator to a gunner. Gunner as in laser shooting an artifact for it latitudinal and longitudinal measurements, not gunner as in shooting bad guys Rambo style.

Yo

Once everyone has gathered their appointed equipment the team is divided into two excavating teams. Since there are two open sites that need to be excavated the team is divided using again a bi-weekly rotational schedule. The first and most prominent of the two sites is PP56, the other smaller site is known as Vleesbaai. After everyone knows which site they have to go to and have all their equipment, the cars get packed and off we go!

Vleesbaai
PP56

On average it takes about 15-20 minutes to drive up the coast to each of the sites. This is one of my favorite times of the day. I get to sit and listen to some oh so hip tropical house jams with the mandatory trumpet/flute solo and relax. I know Kygo’s music is pretty sweet on its own, but what really makes this part of the day my favorite is being able to watch the rest of the world wake up. There’s something beautiful and personal about watching everyone prepare for the day ahead of them. Both teams tend to arrive at the parking zone a little before 6 AM. Since both sites are located on the actual coastline, we aren’t able to drive directly up. This means that we have to pack mule ourselves with our gear and walk to the site. Now if you are at Vleesbaai this is easy, pleasant even. You walk down to the beach and then for a mile or two you stroll down the soft flat beach. PP56, however, is like descending into the depths of Cthulhu’s watery domain. PP56 is a cave site, a cave site located on a jagged cliffside. Just to get down to the beach we have to walk down a ramp so steep cars don’t have traction on it.  Not only that, but once on the beach you then have to scramble up about a ½ mile along the cliffside to reach the entrance to the cave. Now, add a 50lb pack full of equipment worth more than your college debt and your set!

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When you do manage to get to the site, everyone divides up to their designated sections or stations and sets up. And, so the day starts. For a total of 9 to 10 hours, we work like a human version of an ant hill. Excavators, carefully measure, dig and plot any finds. Gunners, constantly take measurements. And, directors, analyze data and supervise. Throughout the day we get coffee breaks to reboot our caffeine intake and stretch our limbs.

Scrub a dub dub time to get in the tub

At 4:50 PM everyone’s internal factory bell rings signifying the end of the day. We pack up our equipment, walk back to the cars, and drive back to the lab to put everything away. It’s 6:00 PM by the time we arrive back at the house and with only an hour before dinner it’s like Black Friday in a mall. Everyone is trying to get a shower to try and rub away some of the dirt that’s decided to become our second skin, but unfortunately not all do. If I’m lucky I manage to snag a shower, but most of the time I just wait until after dinner when the hot water tank has a chance to refill itself.

Once everyone returns back from dinner fat and happy, we pack our lunches, call our loved ones and relax. However, the work isn’t finished. At about 10 PM we all grab some local beer (or liquor if you are one of the Australians) and spend the next hour bantering and labeling our artifact bags in preparation for the following day.

Is Butter a Carb? What are macronutrients

All foods possess certain amounts of both macronutrients and micronutrients (vitamins). The makeup and availability of these two nutrient forms determine the degree of which foods are better or worse for our health (36). For example, iceberg lettuce is predominantly composed of water and fiber (~95%), making it practically crunchy water. The nutrients available in the lettuce are not readily accessible since our body must sift the nutrients from the water resulting in nutrient loss (38). Additionally, the number of nutrients present within a food source can affect its nutritional value. Meat has little or no carbohydrates; it’s just protein and fat. As a result, a nice ribeye steak can provide an excellent source of protein and fats, which are necessary for our bodies basic function. However, if someone only eats steak, they are no longer receiving an adequate amount of carbohydrates, which can result in potential health problems. However, while it is important to consume all three of the macronutrients, the quantity in which they can be consumed can vary drastically. Humans are generalists; we can adapt to very diverse environments (31). The Hadza populations consume a 95% carbohydrate based diet, while the Northern Inuit populations subsist on a 95% protein and fat based diet (29). The morphology of our gastrointestinal system, dental morphology, and tool technology have allowed us to consume a wide array of foods while maintaining health across vastly different environments (31). So, whether you eat more like a Hadza, Inuit or somewhere in-between, let us look into how each of the three macronutrients function.

A Hadzabe from Northern Tanzania.
Inuit women and child in traditional clothing.

“You can run, but you can’t hide!” If carbohydrates could talk, that’s what they’d say. The most common of the three macronutrients, carbohydrates can be found almost in everything. From fruits to dairy products, this macronutrient carries important nutrients, such as vitamins, minerals, dietary fiber, etc. into the diet (38).

Carbohydrates are composed of three subgroups: monosaccharides, disaccharides, and polysaccharides.  Often considered to be the building blocks of carbohydrates, Monosaccharides are simple sugars (glucose, fructose, and galactose). This means that they do not require any form of catabolic reactions in order to be digested and absorbed into the body. Disaccharides are two bonded simple sugars (sucrose, lactose, and maltose.) which require hydrolyzation in the small intestine to be digested. Polysaccharides create the longest chemical chain of bonded sugars. They come in two forms: starchy and non-starchy polysaccharides. Starchy polysaccharides are commonly found in the underground portions of plants, such as potatoes, and store the plant’s nutrients. To digest these, the body must use amylase enzymes located in the pancreas and saliva to help reduce the starch into simple sugars which are then hydrolyzed in the small intestine. Non- starchy polysaccharides or fiber, provide the plant with overall body and cell structure (36). They are the most abundant of all forms of carbohydrates, coming in four different forms: pectin, hemicellulose, cellulose & lignin (38). While pectin & hemicellulose can be digested, cellulose & lignin require bacteria located in the stomach to break them down through fermentation.

Lipids, also known as fat, and protein, although not as common as carbohydrates, are just as important. Lipids help to create long-term energy stores (Triglycerides) through anabolic reactions, carry vitamins, and influence our neurotransmitter levels which help regulate reproductive hormones in our body (38). There are four types of lipids: saturated, cholesterol, mono/polyunsaturated, and trans unsaturated. Both saturated lipids and cholesterol are mainly found in animal fats. Both monounsaturated & polyunsaturated are commonly found in vegetable oils and can have positive effects on our heart health (like Omega-3). Trans unsaturated lipids are the bad guys of lipids. They are unsaturated fats that have been altered by adding hydrogen and are known to cause unhealthy changes in cell membranes. 

Protein helps with tissue replacement and is critical for growth and reproduction (32&36). It is composed of different types of amino acid chains.There are a total of 20 different types of amino acids, 9 of which are essential for us that we can’t produce them in our bodies, and 11 which are non-essential that we can produce in our bodies (36). There are two types of protein sources: complete and incomplete. While there are many ways in which we can find all 9 essential amino acids in our diets, all 9 can be found in animal protein and soybeans. So, now that you know all about macronutrients and why butter is not a carb, we must next look at how macronutrients have helped mold us into the Homo sapiens we are today.

 

Lucy’s Paleo Diet: How teeth reveal important insight into early hominin diet

Diet is a fundamental aspect of an organism’s ecology. The food an organism consumes provides its body with nutrients to function and maintain basic life. Diet is also indicative of the environment in which an organism lives. In today’s western society, we are often easily able to access specialty foods from all over the world. Living in the diverse community of Boulder, CO, I could enjoy Ethiopian, Italian, Tibetan, Vietnamese, Chinese or German food, all within a short distance from my home.  However, our early hominin ancestors did not have the luxury of such variety. As a result, the changes researchers have observed in hominin diet have been hailed as key milestones in human evolution.

What the world would be like if pizza grew naturally?

When observing early hominin diets, paleoanthropologists generally create four principal groups of interest: The Miocene-Pliocene probable hominins (about 7-4 MYA), the Pliocene-Pleistocene ‘gracileaustralopiths (about 4 MYA), the Pliocene-Pleistocene ‘robust’ australopiths (about 2.5 MYA) and the earliest members of Homo (about 2.5 MYA)(18).

 

Prior to the introduction of new methods in the last several years, theories regarding the diets of these groups were predominately based on the overall shape, size, and structure of teeth, resulting in paleoanthropologist’s observations being limited to only one lens: morphology. Observations of the recovered teeth of Miocene-Pliocene probable hominins like Sahelanthropus tchadensis, Orrorin turgenensis, and Ardipithecus ramidus, indicated smaller and thinly enameled molars similar to extant chimpanzees. As a result, paleoanthropologists suggested a diet primarily composed of fleshy fruits and soft, young leaves for the Miocene-Pliocene probable hominins. 

Due to the long history of primates consuming fruits, primates are no longer able to produce vitamin C within their bodies. OH FRUIT!

The later gracile and robust australopiths, however, exhibited a craniodental morphology with thickly enameled, large, flat cheek teeth, combined with heavily built crania and mandibles relative to extant apes (6). This led many researchers to believe that there was a shift from the previously softer diet to one dominated by hard and abrasive foods like brittle nuts and seeds, or underground storage organs (USO). The more robust australopiths (Paranthropus) showed even larger teeth with massive chewing muscles. This led to the notion that they consumed even harder foods and/or relied more heavily on hard foods than their gracile counterparts (1)

P. boisei’s molars could be up to the size of a quarters diameter. Left-P. boisei, Right-H. sapiens.

When observing the earliest members of our own genus, Homo, evidence showed smaller cheek teeth, thinner enamel and a higher occlusal relief compared to their australopith predecessors. Additionally, evidence of tool use has been associated with Homo. This steered many paleoanthropologists to believe that Homo was able to process a broader range of foods, like meat and USO’s and that the morphological differences were caused by selective pressure resulting from extraoral processing (11&7). While all of these observations hold scientific truth, they are limited in their accuracy due to the evidence relying only on morphology.

Underground Storage Organs

Thankfully, over the last couple of decades, our understanding of early hominin diet has advanced substantially as a result of new methods, dental microwear, and stable isotopic analyses, as well as the discovery of new fossil species and additional specimens. Improved paleoclimate and paleoenvironment reconstructions have also contributed to a broader understanding of hominins. These advancements have allowed researchers to better define and alter previous theories arriving at a more comprehensive understanding of early hominin diet.

Have you ever eaten popcorn and accidentally bitten into an un-popped kernel? If you have, you’ve likely experienced a form of dental microwear. Dental microwear are pits and scratches that form on a tooth’s surface as the direct result of its use. When you bite down on an un-popped kernel or any hard and brittle food, the microwear left behind resembles a pit. If, however, you are trying to shear through a tough food like beef jerky, the microwear patterns will instead show long, parallel striations (20, 6 & 16). Our teeth, like all mammal teeth, tend to show a strong and constant association between microwear patterns and food fracture properties, thus allowing researchers to trace the chewing events of an individual. Unfortunately, microwear is fleeting, since individual features are replaced by new ones as the tooth naturally wears down. This effect is also known as the “last-supper” phenomenon because when paleoanthropologists look at tooth wear in early hominins they are observing the diet in the days or weeks before the death of the individual (18).

C4 plants-Wetland grasses

The phrase “you are what you eat” can be directly applied to stable isotope analysis. Stable isotopes, which are found within every item that an individual consumes, will be incorporated into the teeth and bones of that consumer. Stable isotopes are atoms whose nuclei all contain the same amount of protons, but different amounts of neurons (8). When observing stable isotopes in hominin paleodietary studies, carbon isotopes are typically chosen.

C3 plant-podalyria sericea

This is due to carbon isotopes showing the type of photosynthetic pathways for a use, relative to proportions of carbon- Carbon 3 (C3) or carbon 4 (C4) (14&18)C4 indicates tropical grasses while C3 indicates trees, bushes, and forbs. Now, you might wonder how we can reconstruct the diet of early hominins when we are only looking at flora. Well, just as the phrase “you are what you eat” suggests, carnivores will show different proportions of carbon depending on the proportions that their prey consumed. Simply put, biological anthropologists can determine what species eat by examining each trophic level on the food chain.

Both microwear and stable carbon isotope studies have challenged many long-held assumptions regarding early hominin diets. Previous assumptions that the craniodental morphology of early hominins evolved as the result of their increased consumption of hard, brittle foods due to the expanding of open savanna landscapes is either incorrect or just too simplistic. For example, none of the teeth of gracile or robust australopiths show the heavily pitted surfaces that would indicate their being hard-object feeders, as originally expected given their morphology (14). It has been suggested that the distinct differences between microwear and morphology relate to ‘fall-back’ foods, meaning that australopith dental anatomy evolved to cope with harder more brittle foods consumed when their preferred foods were unavailable within their environment. Additionally, carbon isotopes show that Ar. ramidus, the earliest taxon analyzed to date, had a C3 diet much like that of savanna chimpanzees.

Ar. ramidus

There also seems to be a geographic influence on australopiths diets, with the microwear of eastern African Australopithecus and Paranthropus being less complex than that of their South African cousins. Also, within species, like Paranthropus, differences in carbon isotope compositions can be seen (1). For example, P. robustus has been noted to have consumed more than 50% C3 foods, but also substantial quantities of C4 foods. P. boisei, however, had a diet of about 75 to 80% C4 plants, which is similar to grass-eating warthogs, and hippos (18). This variation may possibly indicate that a specialized morphological complex can have more than one function and reflect more than one type of diet.

So, as you flip through your magazine in the waiting room of your dentist, learning about how to eat like a caveman, just remember the impact your teeth could have on enlightening our future hominin lineage. Remember readers: brush, floss, and mouthwash your pearly whites, for your teeth could be the future of hominin history!

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It’s all about the tooth, the whole tooth and nothing but the tooth.

Departure: Denver, Arrival: Mosselbaai

Everyone has a place they’d love to visit. Whether it’s standing on top of the Eiffel Tower overlooking the City of Love or diving deep into the crystal blue depths of Australia’s Great Barrier Reef, we all dream of exotic locations. After spending the last 5 years learning and specializing on the origins of our own species, I have since dreamed of visiting the African continent and digging in its rich warm soil. To create my own little part of history, both in the past and present. And now, finally, after years of creating connections and daydreaming have landed on the African continent!

Having flown a total of 9551 miles over the past 48 hours, it was hard for me not to want to kiss the ground. As much as I love traveling, I hate flying. Being cooped up in a chair and having to deal with customs, delays, miss placed league and random searches for 48 hours is my personal nightmare, but one I will gladly succumb to if it allows me to go to new places.

This is my first time on the African continent, making my list of visited continents a little bit larger (only 3 more to go!). Landing in Mosselbaii South Africa I will be spending the next month working as a field excavator for the SACP4 Project. Here we will continue the search for evidence of the oldest instances of marine foraging, ochre use, production of microlithic material and heat treatment on stone tools. In doing this, our team will attempt to answer many unsolved questions surrounding South Africa’s paleoclimate, paleoenvironment, paleoecology, and paleoanthropology.

Our guiding captain of the project, is none other than Professor Curtis Marean, from the School of Human Evolution and Social Change at Arizona State University. Curtis has been actively engaged in debates and studies surrounding the effects of marine resources and socialization on early Homo sapiens (1& 2). An engaging speaker and writer, and overall very friendly guy, I am extremely honored and excited to be working by his side. As for the team, we are a large group of about 30 individuals spanning the entire globe. A large portion of the group hail from Australia and many have been working on this site for the last couple of years. While it is always intimidating meeting new people, especially people who already have a friend group, everyone is open and friendly.

Due to the nature of working on field sites (long arduous hours and close quarters), the team lives, works, and breathes as a unit. Think of Jersey Shore minus the hot tub and most of the drama. As a result, typically the first night on new field sites, the briefing meeting is supplemented with local beer and food and everyone relaxes, settles in, and get to know each other.Our first night in South Africa was no different. Everyone gathered around a large outdoor fire pit to enjoy local BBQ known as braai and some local beers like Amstel, Black Label, and Carlsberg. When everyone was stuffed with good food and drink, Curtis began the briefing on local culture, customs, site layout, and workload. Warmed by the fire pit on my back and surrounded by my new family for the next month and a half, I couldn’t help but think how familiar it all felt. I may be 9551 miles from all that I know, but here in this moment, I know I’m home.

Paired with an Amstel radler and I’m in heaven.

 

 

#Takemeback: How faunal material can recreate the paleolandscape

As a species, we humans spend nearly as much effort looking behind us as we do in front of us. From an early age, we are taught the history of our communities, our countries and even, sometimes, our evolutionary history. And, our fascination with the past is not limited to education, we may also venture into #Takemeback, hoping to experience the thrill of hopping into another era. But, why do we focus so much on things of the past? Past experience lends us insight into what may happen next. We humans value this information, and as such, collect, read and learn about it in hopes of improving our future. But, how do we learn when there is nothing to collect or read?  

Paleoanthropologists have always been curious about where it all began, striving to piece together how we, as a species, metamorphosed from small, hairy, arboreal creatures into large, hairless, gangly bipeds. And, while paleoanthropologists are able to use hominid fossil remains, to understand the past they can only do so to a certain extent. Hominid fossil material typically makes up less than 1% of all material discovered in an assemblage (3).

Teeth are one of the most common hominid finds.

Additionally, the material will only show morphological characteristics. As a result, it becomes nearly impossible to exclusively use hominid material to research and understand why we as a species evolved. So, in order to better understand and answer questions of our evolutionary lineage, paleoanthropologists often use faunal material in addition to hominid fossil material. By using these additional materials, paleoanthropologists attempt to recreate the environment and landscape our early ancestors were living in, allowing them to better understand how certain adaptive traits, such as bipedalism, have emerged and why.  

A tenet of Darwin’s natural selection states that if an organism is unsuited to its environment, it will reduce its overall reproductive fitness, eventually decreasing its chance to pass on its genetic material (15 & 22). Organisms that are better suited to their environments will increase their overall reproductive fitness, thus increasing their chances of passing on their genetic material. When observing hominid sites, paleoanthropologists often pull from Darwin’s concept of natural selection in order to create hypotheses about certain adaptations found in fossil fauna that can then be related to the paleolandscape. These hypotheses are based on comparative studies conducted on extant fauna residing in similar environments, as the fossil fauna (13 & 19). One such hypothesis is known as the savanna hypothesis which stipulates that extinct fauna will show a gradual increase towards adaptations for more arid and open environments in certain areas after the late Miocene (11.6-5.3 MYA). These adaptations can be seen in the form of speed and endurance. Take for example two hominid species.

Hominid A shows higher amounts of arboreal adaptations whereas hominid B shows higher amounts of bipedal adaptations. If we place both of these hominids in an open and arid environment it is more likely that hominid B will hold a higher reproductive fitness compared to hominid A. Why you ask? Because, if hominid A holds adaptations that are best suited for an environment abundant in trees but is now in an arid and open environment with little tree cover, it’s going to have a bad time.

Faunal reconstructions have been made for many different sites, including the Omo, Sterkfontein, and Swartkrans (4, 23 & 9). Within the Omo site region, for example, a great deal of faunal material was recovered spanning a timeline from 4-1MYA. The material discovered, including both faunal and hominin specimens, showed clear indications of a gradual shift to a more arid/open environment. The lower strata showed high amounts of Tragelaphini and some species of Reduncinae. These were antelope which resided in woodland environments.

Reduncinae
Tregelaphini

In the upper strata, however, a shift towards more digitigrade and hypsodonty mammal species like Elephantidae and Hipparion were found, suggesting a more open environment (3). As for hominid evidence, in the lower strata Au. afarensis was found, which was thought to have inhabited a more woodlandesque environment. But, when moving up in the strata evidence of P. boisei and Homo was found, both of whom indicate some adaptations towards a more open environment (22). Evidence such as this helps paleoanthropologists to better define why certain adaptations can to be. So, while paleoanthropologists can’t actually #Takemeback, they can however #buildthepast.

The Human Color Swatch: How variation affects your skin color

*A note from the Author*

We all know that the issue of race is a delicate subject and one that is unavoidably linked to skin color. This post will not focus on the subject of race, but rather on why we see differences in the color of human skin. Race is a social construct, not a biological one. The color of our skin is not determined by our race, social standing or ethnicity, but rather by the environmental stressors our ancestors were subject to.

Skin color could be humanity’s most visible characteristic. Coming in a gradient of colors, it provides us with a billboard of information regarding an individual’s health, age, and ancestry. However, skin is more than just a walking advertisement. It is the vanguard of our bodies, protecting our delicate innards from many forms of physical, chemical or microbial harm (23). Skin also provides critical information about the ambient environment and any objects touched. Additionally, it helps regulate body temperature by sweating or by either increasing/decreasing blood flow within the blood vessels located in skin layers.

The skin is divided into two main groups of layers: the dermis and the epidermis. The dermis consists of a thicker inner layer of skin, whereas the epidermis consists of a thinner outer layer of skin. Within the epidermis are four layers of skin. The most important of these layers, in regards to skin color, are the melanocytes layers since they host melanin, the primary pigment found in the body (24).

Melanin are cytoplasmic organelles called melanosomes. They come in two different forms: eumelanin and pheomelanin. Eumelanin consists of the brown and black pigments, whereas pheomelanin consists of the red and yellow pigments. As a result, if an individual has more eumelanin they will exhibit darker skin color compared to someone with more pheomelanin. Additionally, within skin color, there are also two skin types that react differently. The first is constitutive skin color which consists of your genetically predetermined skin color in absence of any external stimuli, like sunlight (24). Simply put, this is the skin color you were born with, the original #nofilter, #no makeup look. The second is known as facultative skin color which develops when exposed to any external stimuli, like sunlight. So, that killer tan you got when you went to Bali? That’s your facultative skin hard at work!

Generally, an individual with more eumelanin will exhibit a higher degree of facultative skin color and be descendant from individuals who resided in either the poles or close to the equator. As a direct opposite, individuals with more pheomelanin will exhibit a lesser degree of facultative skin color, and be descendant from individuals who resided below the poles and away from the equator. This strong latitudinal signal is thought to be directly associated with exposure to high degrees of sunlight (23).

Both the poles and the equator present higher more intense degrees of sunlight and UV radiation. As a result, individuals living in these kinds of environments would have had to adapt to more intense and longer periods of sun exposure. It has been proven scientifically that darker skin holds significant benefits towards prolonged and intense sun exposure. Eumelanin prevents more UV radiation from entering the body than pheomelanin. Facultative skin is also more resistant to sunburns, allowing individuals with a higher amount of facultative skin to be exposed to sunlight for longer periods of time. Compared to darker colored individuals, lighter colored individuals tend to reside away from areas of increased sunlight. As a result of not having as much sun exposure, their skin color will adaptively shift to a light color to allow for maximum absorption of solar rays. This allows them to exploit as much sunlight as possible which in certain doses can be helpful for the body and mind. Who doesn’t love a good cat nap in the sun?

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I swear he’s not dead. He just loves napping.

Like all tetrapod’s our skin is made to protect us from harm and is the initial locus for the synthesis of vitamin D (9). Vitamin D is an important micronutrient needed to maintain overall body function and maintenance. It manages calcium in the blood, gut, and brain and helps to provide communication between cells (23&9). Like vitamin C, vitamin D is not produced within the body but instead is primarily absorbed from sunlight. However, if too much UV penetrates the body, damage such as sunburns and cancers can form. So, a balance must be made between the amount of UV penetration and vitamin D synthesis.

Milk is a great source of vitamin D

Since individuals with darker skin color have increased protection against UV radiation, they are unable to absorb vitamin D as effectively as individuals with lighter skin color. Still, individuals with darker skin are able to obtain enough vitamin D, but only if they reside in environments with adequate sunlight. And, since there is a higher amount and intensity of sunlight located in the poles and equator, individuals with darker skin are still able to receive enough vitamin D. On the other hand, lighter skin colored individuals have decreased protection against UV radiation but are able to better absorb vitamin D. But, if lighter skin colored individuals find themselves in areas with higher and more intense rates of sunlight they have an increased risk of obtaining diseases like skin cancer from increased UV absorption.  If dark-skinned individuals reside in areas where there is not enough sunlight, they run the risk of not obtaining enough vitamin D. This can lead to serious deficiencies such as rickets, if not remedied.

As society further develops, it becomes easier for individuals to reside in environments for which their skin might not be best adapted. Darker skinned individuals residing in environments with restricted sunlight may overcome vitamin D deficiency by consuming vitamin D fortified foods, such as milk, multivitamins or vitamin D tablets. Lighter skinned individuals residing in environments with high exposure to sunlight may overcome over absorption of solar radiation by wearing either sunscreen or clothing, thus reducing the surface area exposed directly to sunlight. So, whether you can absorb vitamin D like a boss or thwart UV radiation with a flick of your wrist, each and every one of us shows amazing amounts variability. No wonder we’re able to inhabit most of the globe. Go Homo sapiens, go!

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Don’t Forget to Bring your Trowel! The 101 on Paleoanthropology

Defined as “the study of ancient humans,” paleoanthropology is a branch of anthropology which strives to reconstruct all aspects of human evolution (25). A multidisciplinary field, it combines disciplines such as archaeology, anthropology, paleontology, geology, as well as many others to observe the anatomy, behavior, and ecology across the hominin lineage. By better understanding the hominin lineage, paleoanthropologists attempt to discover how early hominins lived and “how” and “why” certain species evolved in anatomically modern humans, or died out.

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So how do paleoanthropologists begin to answer these questions? Paleoanthropologists use early archaeological, hominin and paleoenvironment evidence, which allows them to begin the process of reconstructing our ancient past. Evidence often includes fossilized bone from both hominins and other animals, lithics, plant and animal matter, footprints, evidence of hearths, butchery marks on animal bones and art (36). https://media.giphy.com/media/xUPGcmF2iGsTGEFVL2/giphy.gifUsing these materials, researchers can then establish hypothesis which can begin to explain the physical and behavioral makeup of early hominins and how it has altered across a spatial and temporal timescale. Going back to our graduate students, say for example one of them discovers an Acheulean bifaced tool along with an extremely “primitive” fossilized hominin hand.

Acheulean biface
Australopithecus Sediba

 

 

 

 

 

 

 

 

Assuming that this graduate student has gained an adequate knowledge of hominin functional morphology, they might note that the dexterity required to create an Acheulean biface surpasses the dexterity found in the fossilized hand. As a result, the graduate student is faced with four potential hypotheses: 1) the tool was not created by the hand of the “primitive” hominin 2) the tool was created by a different hominin species living at the same time 3) the deposit in which the tool and the hominin were found was mixed in with another deposit layer, or 4) the tool was indeed created by the hand of that hominin and all our previous understanding of hand morphology is flawed.

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To locate fossils, researchers typically look for areas which might potentially hold hominin fossils. This can be anything from sediments of the right time period being exposed by natural erosion to educated guesses based on the locations of previously discovered fossil specimens. Fossils are typically discovered in two different locales depending on the region of Africa they are located in. East African fossil specimens are typically located throughout rift valleys whereas in South Africa fossil specimens are mostly found in cave sites. African Rift valleys are caused when portions of earth’s crusts have been pulled apart due to the movement of tectonic plates (40)

Olduvai Gorge in Tanzania, East Africa
Sterkfontein near Johannesburg, South Africa

This then results in deep valley/trench like formations surrounded by large mountain ranges   Fossils, if found in East Africa, will usually be exposed along the sides and floors of the rift valleys due to rivers and streams eroding deep into the sediment layers. In South Africa, fossils are mainly found in caves. This is due to South Africa having large limestone deposits. Since limestone is extremely porous, as rainwater runs through a limestone crack it erodes surrounding limestone, eventually expanding into caves and tunnels. At any sort of cave opening, soil will be washed in from the surface, allowing for hominin remains to be deposited there. Hominin fossils in South Africa are typically found when miners blast the caves in order to attain the limestone or other mineral resources. The famed Taung Child, for example, was discovered at the Buxton limestone quarry in the Northwestern Province of South Africa following a mining blast.

Even after being blown up, it still took Raymond Dart 3 months and a pair of sharp knitting needles to painstakingly uncover Taung Child from the attached limestone.

While hominin fossils are located within caves there is weak evidence which suggests that early hominins used caves as habitation sites (40). Paleoanthropologists actually believe that the majority of hominin fossils found in caves were brought in by leopards, hyenas or bone collecting animals such as the porcupine (37).

https://media.giphy.com/media/3oEhmOCVVhTXA7x3IA/giphy.gif
A lean mean bone crushing machine!

As an apex predator in today’s world, it is often hard to imagine any of our ancestors becoming prey. However, many of our early ancestors were physically, mentally and presumably socially different than ourselves, making them more susceptible to predation. A famous juvenile Paranthropus robustus skull cap (SK-54) from Swartkrans was discovered to have two 6mm puncture wounds-wounds that when paired with the lower jaw of an African leopard match perfectly (33&39). Additionally, there have been some claims to evidence suggesting that Taung Child was killed by a large predatory bird (5&22).

Taung Child (Australopithecus africanus)
Taung Child-Australopithecus africanus

Paleoanthropologists fervently strive to discover fossils and artifacts such as SK-54, as they are a physical evidentiary timestamp of a particular event. Unfortunately, fossils like SK-54 are quite rare and often it is up to paleoanthropologists to hypothesize what occurred over the last 4 million years.  By probing into the past, researchers, like our graduate students, can begin to ask some of the broader questions surrounding our evolutionary history,  and perhaps, glean important information into who we are.

 

Supervillain or Superhero? How autosomal recessive disorders affected human evolution  

Oftentimes in movies, we root for the superhero and despise the super villain. After all, who wants Dr. Evil and Mr. Bigglesworth to dominate the world by turning the moon into a death star? His success wouldn’t benefit anyone other than himself and his cohort of miscreants.  Civilization and freedom would be compromised, effectively squashing humans as individuals. But, by rooting for the devilishly carnal Austin Powers, human civilization is maintained and evil is vanquished. Using a little creative interpretation, we can find these character tropes in evolutionary biology.

A basic belief in evolutionary biology is that a gene will only survive over generations if it can provide some form of advantage to a species (the superhero). If a gene provides a disadvantage (the super villain), such as a lethal disorder or disease, it should eventually disappear from the gene pool. Basically, how many reproductive opportunities a gene provides its carrier will determine its success. However, certain genes, act as both a superhero and a supervillain. As genes combine to form traits, they can sometimes show both positive and negative assets within the trait. An example of this are autosomal recessive disorders, where the amount of negative assets present can provide either an advantage or disadvantage to the carrier. They are the superheroes and supervillains version of our genes!

Typically, humans have 46 chromosomes on which all our genes are located. Arranged into 23 different pairs, one of each chromosomes that creates the pair is passed from your mother or father. 22 of these chromosomal pairs are known as autosomal chromosome. Autosomal chromosomes decide every trait you have aside from gender. When variation within a gene results in a negative trait, and is passed from both parents this is known as a recessive mutation. An autosomal recessive disorder develops when a recessive mutation occurs on an autosomal chromosome and both parents pass the mutation. Even then there is a 25% chance of having inherited the mutated gene and developing the disorder. If only one parent passes the mutation there is a 50% chance of inheriting one of the mutated genes and becoming a carrier.

Autosomal recessive disorders are extremely harmful and deadly to the afflicted. Those burdened with an autosomal recessive disorder find themselves with complicated health issues and shorted lifespans. However, those who are carriers can demonstrate increased resistance to certain diseases. Diving into this lottery of inheritance lets look at the pros and cons of one of these disorders-Sickle Cell Anemia.

Sickle Cell Anemia

Sickle-cell anemia occurs when there isn’t a sufficient amount of healthy red blood cells to carry oxygen throughout the body. Caused by a mutation in the gene that affects hemoglobin, the usual rounded flexible shape of the hemoglobin becomes rigid and sticky, resembling sickles. Mutated hemoglobin, known as hemoglobin S., cause a wide variety of negative complications, such as anemia, pain caused by blocked blood flow, swelling of the hands and feet, delayed growth, increased infection rate, and vision problems. However, when a carrier for sickle-cell anemia, known as sickle cell trait, there is instead an increased resistance to Malaria.

An infectious disease, caused by parasitic protozoans, malaria is transferred to humans only through the female Anopheles mosquito. when infected, the protozoans move through blood vessels to liver cells and reproduce asexually, eventually releasing back into red blood cells to continue their life-cycle. If a host has the sickle-cell trait however, the defective hemoglobin S present within their body will rupture, preventing the malaria parasite from continuing its cycle. Unfortunately, anyone afflicted with sickle-cell anemia who contracts malaria become more vulnerable, since all of their red blood cells will sickle, causing a lack of oxygen throughout their body.

What Does This All Mean?

Its clear that autosomal recessive disorders are devastating and deadly and being a carrier provides protection against some pretty terrible diseases. But, most interestingly is who these particular disorders and diseases affect and why. Populations most affected by Malaria show higher rates of Sickle Cell. However, it is important to note that a higher occurrence of a specific disorder is not directly related to a particular race, nor does it indicate a certain population is at a disadvantage to others. Rather, it is directly related to the geographic region, and environmental pressures, an individual’s ancestry is adapted to. If a population group lives in an environment where potentially dangerous diseases are prevalent, the fitness of that population will select for traits that provide a genetic advantage. Over generations, that population will be more resistant and at an advantage for living in that particular environment.

When looking at sickle-cell anemia and sickle cell trait, higher percentages are found among peoples in Sub-Saharan Africa (up to 30% in Nigeria alone), the Chalkidiki district of Greece (18-32%), and on the Eastern Province of the Arabian Peninsula (20-30%) Within these geographical locations, and consequently among their populations, higher rates of malaria are seen. However, these are not the only locations in which we see sickle cell. High rates of sickle cell can also be seen among African American populations in the United States. This is attributed to the dispersal of population groups specifically associated with higher rates of sickle cell. Reviewing historical documents has enabled researchers to track these movements of large populations groups. Looking at records documenting the United States Atlantic slave trade many slaves came from the coasts of the Sub-Saharan African region. Movement of sickle cell has also been documented during the 1950’s large-scale immigration from the Arabian Peninsula into Germany of Turkish nationals.

Spread of Malaria Worldwide
Spread of Sickle Cell Trait Worldwide

While genes that result in autosomal recessive disorders negatively affect the individual who carries them, the more the common carriers of the disorders are protected from other diseases. This advantage allows the carrier to reside in environments with strong selective pressures without hindering their fitness, enabling them to effectively pass on their genes to future generations.


Though the majority of individuals will never experience the negative effects of having an autosomal recessive disorder, we must all strive to help resolve the calamity of these supervillain genes. 

  • To learn more about autosomal recessive disorders click here.
  • To learn more on how sickle cell kicks malaria’s metaphorical tooshie click here.
  • To learn more about what malaria is click here.
  • To learn more about the evolutionary link of sickle cell and malaria click here.
  • To donate to fight against autosomal recessive disorders click here.

One Dog, Two Dog, Big Dog, Small Dog: The forces of evolution

Sitting on a park bench one day, you notice a Great Dane and Chihuahua happily sniffing and circling each other in mutual greeting. Staring, you notice how different they are and wonder how it is even possible that they are still part of the same species. This difference you see is known as variation. The World Canine Organization recognizes 339 individual breeds of dogs, all of which exhibit unique forms of variation. While many of the variations we see in those 339 breeds are the result of domestication and purposeful breeding, variations within a more natural environment still occur. Differences in physical and genetic makeup exist across all organisms. These differences or variations allow for a species or population group to become better adapted to certain environmental stressors. There are four ways in which variation can occur: mutation, gene flow, genetic drift and natural selection. 

Mutation

Who mutated best? Night Crawler or Andorian?

Thanks to creative sci-fi films, the word ‘mutation’ may prompt us to picture genetic monsters or creatures with two heads, one eye and an array of superpowers. However, the majority of gene mutations are subtle or even undetectable. Gene mutations occur when errors are recorded within DNA during the cellular replication process. There are two classifications of gene mutations: somatic and hereditary.

Somatic mutations are the more common of the two, and occur during the lifetime of an individual. They are typically caused by environmental factors, like UV rays from the sun, or are the result of spontaneous errors made when adult cells divide. While somatic mutations don’t directly affect the entire genome and can’t be passed to the next generation of the individual, they will be present throughout the descendants of the original mutated cell which sometimes cause cancers. Hereditary mutations are passed from parent to offspring. These occur in the cells of the sperm or egg. If either an egg or sperm cell holds a mutation, the offspring from the fertilized egg will have the mutation present in virtually all of the cells of it’s body. Although rare, by creating new genes and alleles, hereditary mutations have the ability to introduce new variants, thus potentially increasing genetic differences between populations. So, while it is highly unlikely that you are a mutant with awesome powers, it is not impossible.

Gene Flow

As humanity becomes more unified, so do our genes. When an organism migrates or moves, from one population to another, it allows its genetic material to move as well. Known as gene flow this can occur in many different ways depending on the organism itself. For example, pollen from one group of flowers may passively be transported to another group by means of insects, birds or wind, whereas humans may actively elect to move to a different region and population group.

The ability of genes to move into a new population group can be a very important source of genetic variation, especially if that gene version did not previously exist within a population. In the Amboseli basin in Kenya, mating between the yellow and Anubis baboons has allowed for the transferring of genetic makeup between the two different subspecies creating maturational and reproductive advantages. Although gene flow may seem like an easy way for organisms to transfer genetic material, barriers can block the amount of flow a population may see. There are two types of barriers that can affect gene flow: Allopatric speciation and sympatric speciation. Allopatric speciation is when gene flow is blocked by a physical barrier such as a mountain range, large body of water, or man-made obstacle. Sympatric speciation, barriers occur due to gene incompatibility. This typically arises when two different species originate from the same ancestral species but are different enough genetically to not be able to successfully reproduce. Limitations in reproductive success can be caused by incompatible genetics, fragmentation, different social behaviors or hybridization. A good example of this is the Liger.

Genetic Drift

All humans have two copies of every gene; one from their mother and one from their father. In reproduction, only one gene copy from each parent is transferred to their child. Like flipping a coin, each gene copy has a 50% chance of being inherited by you. However, the outcomes of what a child will inherit are not always the same. This is because the outcome is dependent on whether a gene pair is heterozygous (carries two different genes), homozygous (carries two of the same genes), dominant (only one gene needed to show) or recessive (both genes need to show). Known as Mendelian inheritance, certain gene pairs will be more likely to be inherited due to their physical makeup and probability. The ability to examine certain genotypic outcome probabilities can be done through by using a Punnett square.

So how can the frequency at which you receive gene pairs affect the evolution of your entire species? Well, frequencies of particular gene pairs can change from one generation to the next due to chance events that affect the reproductive success of certain individuals. Random occurrences that affect the genetic change within a population is known as genetic drift. As random occurrences continue to affect the variation of one population group, the differences between that group and another will expand creating drift. In 1811, the first specimen of the peppered moth (Biston betularia) began to appear in Manchester, England. A light bodied moth with black speckling, it was well adapted to blending in with the light colored lichen and tree bark found in the area. The majority of the moths showed this lighter dominant color, however, a darker variation of the moth existed, as well. Unfortunately for them, their dark coloration made them unable to blend into their environment, resulting in their being prone to predation . As a result, the frequency of dark coloration was about 0.01%. However, with the establishment of the Industrial Revolution, many of the trees became covered in soot resulting in a massive shift in how the environment appeared. And, like a classic underdog story, the light-colored moths became prone to predation decreasing their population, while the darker peppered moths camouflaged better in the pollution and succeeded in increasing their frequency to approximately 98%.

Natural Selection

Natural selection, a theory developed by Charles Darwin, focuses on variations which are directly caused by environmental factors relating to an individual’s fitness within a population group. While fitness may bring to mind athletic individuals, fitness from an evolutionary standpoint instead focuses on the reproductive success of an organism. For example, if humanity was all of a sudden restricted to living in caves, taller individuals might hit their heads on low ceilings, knocking themselves out and limiting mating opportunities. While, shorter individuals who were not at risk of hitting their heads, might be able to spend more time mating, increasing their overall fitness. The better suited an organism is to its environment, the higher its probability to pass on genes to its offspring, gradually increasing the amount of that particular gene within the population. As a result, our cave population would show an increase in shorter individuals compared to taller people across the next generations.

So now as you sit back on your bench all knowing, you wonder which evolutionary force created the doggie variation you’re seeing. Is it mutation? Gene flow or drift? *Gasp*…could it be natural selection?! While you may or may not ever discover which evolutionary force created all of the wonderful dog breeds we see today, remember this, you are in a dog park surrounded by happy dogs of different sizes, shapes, and colors. Now get off your bench and play with the dogs!


Want to learn more about what you just read? Look no further!

  • For a list of 339 different dog breeds click here.
  • To learn more about mutation click here.
  • Want to know more about sympatric speciation click here.
  • For more on the gene flow between yellow and anubis baboons click here.
  • To learn more about the history of the pepper moth click here and here.