Featured

My Cousin Sahelanthropus: How the discovery of Sahelanthropus tchadensis established a lineage

Image result for sahelanthropus tchadensis
I just never actually “seen” a grit before.

Toumai is our first cousin Vinney. Discovered in 2001 by French paleontologist Michel Brunet and his team of four at Toros-Menalla in Chad, West Africa, Toumai dates around 7 million years (MYA), making him the oldest possible hominin ancestor to date. The discovery of Toumai (TM 226) led to the establishment of a new species known as Sahelanthropus tchadensis. Unfortunately, as is often the case with extremely old material, limited fossil remains are found. This, combined with the fact that many early hominids show both chimpanzee and human traits, complicates any assessment done on a specimen, often resulting in disagreements between researchers. Like many others, S. tchadensis falls victim to these restraints. Since its discovery in 2001, only nine cranial specimens, one of which is Toumai, have been recovered. Due to the limited nature of the assemblage, many researchers are wary of classifying directly under the hominin lineage. Although limited, strong evidence for hominin traits can be seen, resulting in S. tchadensis being placed as a possible hominin within the lineage.

Generally speaking, the cranium of Sahelanthropus is orthognathic in the facial region with a small ape-size braincase (320-380cc), and a long and narrow basicranium (Bruent et al. 2002 & Zollikofer et al. 2004). Additionally, evidence for a thick and continuous supraorbital torus, a small, posteriorly located sagittal crest and large nuchal crest (in presumed males), a large mastoid process can be seen. When observing the craniodental morphology of Sahelanthropus, evidence shows a narrow U-shaped dental arch, relatively small incisors, mesiodistally longer upper canines with abundant apical wear, and no lower diastema between the canine and first premolar. Also, molars show low rounded cusps with bulbous lingual faces with an enamel thickness that is intermediate between chimpanzees and later Australopithecus (Bruent et al. 2005).

S. tchadensis also shows a more anteriorly placed foramen magnum suggesting bipedalism, a trait that is considered to be the prime indicator of a hominin. However, due to the limited amount of fossil material and a lack of postcranial remains, the bipedality of S. tchadensis has been hotly debated. Additionally, a very large supraorbital torus (brow ridge) and a more orthognathic face is noted on Toumai. This is unexpected since these features do not appear until the establishment of the genus Homo at around 2MYA. While all these traits have helped to place S. tchadensis on the hominin lineage, other more chimpanzee-like traits have helped remove S. tchadensis from the lineage. Traits such as an enlarged premolar complex, thin enamel on the cheek teeth, a premolar 3 not resembling at premolar 4 and a small cranial capacity (about 360ml) have pushed S. tchadensis away from the hominin lineage.

to be human or to be chimp, what will be folks?

Chimpanzees are our closest cousins within the Primate Order. In fact, we shared a common ancestor for millions of years before eventually splitting into two separate families and developing our own derived traits. These differing traits have allowed us and our chimp cousins to each best exploit the environments in which we have resided for millions of years. For chimpanzees, the traits are often associated with more arboreal forested environments, whereas for us, these traits are better adapted to more open arid environments. By linking these traits with geological and paleoecological studies, researchers can approximate where the split between chimps and us occurred. It has been estimated that the split occurred around 8-6 MYA, thus, it is not surprising to see both human and chimpanzee traits within S. tchadensis. Since S. tchadensis falls close to the initial split, and since the process of adaptation can take millions of years, it is expected to see both human and chimpanzee traits. So, while Toumai never bailed us out of a crime, he did expand our understanding of the split between our chimp relatives and us.

 

Citations:

  1. Brunet, M., Guy, F., Pilbeam, D. et al. 2002. A new hominid from the Upper Miocene of Chad, Central Africa. Nature. Vol. 418: pp 145-151
  2. Wood, B. 2002. Hominid revelations from Chad. Nature. Vol. 418: pp 133-135
  3. Zollikofer, P. E. C., Ponce de Leon, S. M., Lieberman E. D. et al. 2004. Virtual cranial reconstructions of Sahelanthropus tchadensis. Nature. Vol 434: pp 755-759
  4. Brunet, M., Guy, F., Pilbeam, D. et al. 2004. New material of the earliest hominid from the Upper Miocene of Chad. Nature. Vol. 434: pp 752-755
  5. Brunet M., Guy F., Pilbeam D., Mackaye H. T. et al. 2002. A New Hominid from the Upper Miocene of Chad, Central Africa. Nature. Vol418: pp 145-151
  6. Bruent M., Guy F., Pilbean D., Lieberman D. et al. 2005. New Material of the Earliest Hominid from the Upper Miocene of Chad. Nature. Vol. 434: pp 752-755
  7. Wood B. 2002. Hominid Revelations from Chad. Nature. Vol.418: pp 133-135
  8. Zollikofer C., Ponce de Leon M., Liberman D., Pilbeam D. et al. 2004. Virtual Cranial Reconstruction of Sahelanthropus tchadensis. Nature. Vol. 434: pp 755-759

 

This is Russia: Arriving at the Home-stay

Before arriving to Russia, Artemi our professor had given everyone the locations of their home-stays as well as their home-stay families. I was to be residing with an older woman named Marina who lived just off of Vosstaniya Square on Goncharnaya Street. It’s about a 35 minute drive without traffic from the airport to Goncharnaya square without traffic. My taxi driver, he made it in under 25 minutes. To say we were speeding was an understatement, we were flying down roads weaving between cars and people at such an alarming rate you’d think we were participating in a formula 1 race.  On top of it Nevsky Prospect was having a running tournament down the avenue, but nothing was closed. So, you have drivers and runners bobbing and weaving down the same road all in a hurry. My taxi driver at that point was half out of his drivers side window, one hand on the steering wheel the other shaking in a fist yelling expletives at the runners while also reassuring me by calmly stating “Don’t worry, this is Russia” all while still speeding. It. Was. Madness.

Russia is not only a country, its a state of mind.

When we finally screeched to an abrupt stop in front of the alley the home-stay, an elderly woman with a little Yorkie in her arms was there patiently waiting. Marina has a sweet full face with bouncy curls. Her Yorkie, Boris, has a tiny pink bow holding up if own curly mane and looking very much like the man of the household. Both, spoke very little English. Thankfully, I am not the only student staying with Marina and Boris so between the two of us we are able to communicate with Marina. In the first few minutes of interacting with the two Russians I can already tell we will be getting along well. Marina treats us like her own children, feeding and fussing over us as we settle in. Boris, sniffs everything entering into his domain eventually settling in his pink and green plaid dogie bed and looking at us with mild indifference. With our bags unpacked and full bellies Courtney and I share in our excited jitters of finally arriving and what to expect for our coming semester at Smolny Institute.

Image result for Smolny Institute.
I feel like a boyar attending this school!

Swiping Right on Russia: Arriving in St. Petersburg

I never thought in a million years that I would be so attracted to Russia. Throughout my life, I have swiped left and right on countries, I deemed attractive: Italy, swipe right, Brazil, swipe right, Russia? Ehhh, let me look at their profile… For many of us, we establish a baseline of what we deem exciting and exotic places to travel. Often times these places are well known, easy to access and both culturally and economically attractive. However, simply blind sighting ourselves to our idealist country mentality we can miss out on all the other countries equally or more intriguing. I can’t tell you why I ended up taking my first class on Russian History, but I can tell you that it moved me so much that in a blink of an eye I was double majoring in Russian Studies and headed to St. Petersburg.

Spending a good 18 hours flying across the globe I had some moments to reflect upon my decision to spend a month and a half on the Motherland. Did I remember to bring my adapter? Is it really as Russian as everyone says it is? Shit. I have to speak Russian! Landing in Pulkovo International Airport I suddenly became hyper-aware of how much more time I should have spent learning the Russian language. Everything was in Cyrillic and all of it was above my rudimentary “let’s travel” chapter from my second year of Russian. Luckily Artemi, our history teacher and professed deda of the trip, made sure to give everyone a simple plan of attack on how to navigate to our meeting point, find the Starbucks.

Image result for russian starbucks
I’ll take my skinny vanilla soy latte now.

Once everyone accounted for and caffeinated we headed towards the doors and before even crossing the boundary into the country you could smell them before you saw them…Flowers. Flowers everywhere. Daffodils, roses, daisies you name it. We were surrounded by people holding beautiful bouquets of flowers, anxiously awaiting their loved ones. Everyone was either holding or being given flowers.

Image result for russian bouquet
Don’t worry, they will still count and tally all the flowers and the percentage of roses to babies breath before determining your social valor.

One of my favorite things about Russia is its strong attachment to tradition and cultural heritage. For centuries many cultures around the world have strong affiliations with the tradition of gifting. And, while many countries no longer practice this tradition, in Russia it is alive and well. So much so that the number, types, and color of the bouquet hold significance.  For example,  an odd number of flowers are used for the dead & placing on graves, whereas an even amount of flowers are for the living or a happy occasion. So, should you ever find yourself facing a Russian with flowers always remember:  even is for the livin and odds for the dead (I never was good at rhyming). Buzzed with the coffee in our veins and dazzled by the field flowers everyone prepared to step out of the airport and onto the streets to Russia; all hoping to discover why we all came to this expansive motherland and just what else lay ahead of us.

The Three B’s of Hostels: Beer, Bunk Beds and Breakfast

You’ve already shelled out over a thousand dollars to get to your dream location and still there’s more to pay! What started out as an exciting soul searching adventure is now turning your wallet into a barren landscape. Paying for lodging, food, activities, and souvenirs can quickly rake up your precious dollar bills. And, if you’re not careful can overextend your travel budget. However, traveling doesn’t have to be overly expensive for you to have a good time. There are many ways in which to hop, leap, skip and tiptoe around travel expenses and today I am going to talk about one- Hostels!

Get energized at the Generator located in the very heart of Paris.

What Is A Hostel?

Hostels, also known as youth hostels, are the holy grail for the budget traveler. Like the love child of a hotel and bed and breakfast, hostels are a budget-friendly type of accommodation which focuses on maintaining a shared social experience. While the majority of hostels will offer a couple of private room, their primary accommodation is shared rooms with enough bunk beds to house a small army of travelers. Rather than paying for a room like you do with hotels, in hostels you only pay for the bed and sometimes food. As a result, privacy is limited, but at an average cost of 10-30 dollars a night and the added mix of a thriving social scene, it’s pretty worth it.

No two hostels are alike, but for the most part, they usually offer several options for the type of dorm room you stay in. Typically, there will be all male and all female rooms but mostly they are also unisex. These rooms are great for when you’re traveling with a group of friends or with your significant other (should they be of the opposite sex). Rooms will also often vary in the number of people they can hold (around 4-18 people).

Spend the night in a Boeing 747-200 Jumbo Jet at Jumbo Stay in Sweden!

As travel blogger @glographics states “With a hostel, you get half the price for twice the fun.”

How Much Does It Cost?

On average a bed in a hostel will cost you anywhere from $10+/night to $30+/night. Prices are dependent upon the location of the hostel-popular cities will definitely cost more-room size, amenities and overall prices from surrounding competitors. A private room in a hostel can cost anywhere from $40+/night to $130+/night, making it equivalent to a hotel. Even though a private room costs much more than a shared room, you can still save money since hostels typically host a communal kitchen, free wifi and free guided tours of the area.

Next stop Railway Square YHA in Sydney, Australia.

As a general rule of thumb, hostels are one of the cheapest types of accommodations out there because you are sharing space with other travelers.

Who Will You Meet?

The range of people who stay in hostels is as diverse as Crayola’s crayon colors. Most travelers are between the ages of 18-30, but it is not unlikely that you will meet people outside of this age group. From my experience, there is often a lot of Americans, French and Australians staying at the hostels. However, it’s not unlikely that you will meet people from across the globe. Most people tend to stay in hostels for a couple days, however, there are usually a few people who will stay for a month or two. You never know who you are going to encounter when staying in a hostel and personally, this unknown adds an extra element of excitement when traveling.

Come taco about life with other travelers at La Chimba in bustling Santiago, Chile!

Finding An Awesome Hostel?

it is incredibly easy to find and book a hostel. Like, many of the mass booking sites for hotels you see, like hotel.com, hostels have them too. Sites like HostelWorld.com allow you to not only look up hostels in and around your travel destination but also allows you to read past reviews of travelers who have stayed there before. Additionally, you can also filter your search results based on price, room, rating, and amenities, further tailoring your results to what you want.

Get colorized at ETZzz in Bangkok.

Personally, I am a big fan of HostelWorld because it is one of the larger sites and thus has a pretty massive review/community base. Similar to Airbnb, all you do is input your travel dates and location and it will pull up potential hostels for you to view. Accompanied by each hostel are several photos and videos that can give you a better idea of the hostel you are interested in. Once you find the hostel you want to stay in, you book your reservation by putting down 10% of the total payment on your credit card and then paying the rest upon arrival.

Recommended Hostel Booking Sites:

HostelWorld.com

Hostel.com

HostelBookers.com

Hostelz.com

Humans are Friends Not Food: Diving with Great Whites

The Coastline of Southern Africa is well known as the IT place for great white sharks. With hot spots all over Cape Town, it comes as no surprise that a couple miles south from there; Mossel Bai would also have them. But, just because these parts are teaming with the fishy predators, doesn’t mean that I planned on meeting them up close and personal. Don’t get me wrong, I love wildlife and all things natural, but I have no intention of winning the Darwin Survival Award of the year. But, as most field sites go if you either don’t do something a little dumb and crazy or something crazy and dumb doesn’t happen to you it’s not a proper field site. So after a couple beers, an instructional video and 1750 Rand later, my teammates and I are ready to swim with some great whites.

Cape-fur-seal-anterior-view
“And you thought your Mondays were rough”

Sitting on the boat and contemplating my life choices, we jump through choppy waves and head out to seal rock, where the Cape fur seals hang out. Now contrary to Hollywood belief, great whites are very timid and exceptionally picky eaters (i.e. they only like seals, mainly cape fur seals). However, when you bait them in with the smell of sweet, sweet fish guts near their favorite fast food joint (Seal Rock), they arrive with gusto. And, since we plan on joining them a few precautionary measures need to be in place. what say the experts on precautionary measures? A cage, about 8ft long and 10ft deep with an open top and an “oh shit!” handrail on the inside of the cage.  Once in the cage, you hold on to the handrail and doggy paddle until the guide yells “dive!”. At that point, everyone dives underwater and attempts to see the sharks. Now, that seems easy to do, right? Wrong! The water around Mossel Bai is extremely murky and green. None of that Bali crystal clear water here folks! As a result, you don’t see a shark until you are nose to nose with the thing. And, these guys are big, up to 13ft long! Also, to top the experience, Jenny a juvenile great white has earned herself a name by being predictably curious. Often gnawing, chopping and jumping on the cage.

This is why we can’t have nice things Jenny!

For the next 2 hours, my teammates and I took turns screaming, diving and snapping pics of Jenny and her friends. It. Was. Exhilarating. I am no adrenaline junky, but boy was that an experience. Sharks, especially great white sharks, are one of the top apex predators on our planet making it understandable as to why we fear them. But, they are more than just predators. Just like we humans, they are rulers of their own domain. They live, breed, eat, and die in their waters and are just as complex as ourselves. Yes, they can kill you, and yes, they do look like soulless water tanks, but viewing them only as that is wrong. Instead, we should view them as the beautiful, mysterious and powerful animals they are. Except for Jenny, Jenny sucks.

 

Feeling inclined to meet Jenny and her friends?

It’s Jones…Dr. Jones: What is anthropology?

A true anthropologist meticulously maps, photographs, measures, and removes all artifacts. Anthropologists don’t blow up temples, and certainly not to obtain only one artifact! The truth of the matter is that anthropology is not fraught with explosions, cannibalistic tribes or aliens. Rather, the field of anthropology is mostly concentrated on the scientific analyzation of material in order to answer specific questions.

Anthropologists strive to understand what it is that makes us humans human. And, this can be approached through a multitude of different lenses. Anthropologists observe all individuals that form our family order of Primates across the whole of our lineage. Looking at aspects of genetics to culture, there is a huge spectrum to which an anthropologist can observe. Due to the extent of what can be observed, anthropology is generally divided into three main subfields: Archaeology, Biological Anthropology & Cultural Anthropology. While each subfield focuses on a different set of skills and topics, all subfields hold to the same forms of researching standards. So, let us channel our internal Indiana Jones and uncover what is anthropology!

What is Archaeology?

Archaeologists strive to understand human culture by analyzing objects made by people. This is done by looking for objects that indicate human behavior. These objects, known as artifacts, can be anything people made or used. Even the keyboard I used to type this article and the mug my coffee is in could become artifacts, as could almost all of the things we humans interact with. At field sites, archaeologists carefully pull pottery shards, tools, building structures, burial items, food, etc. from the ground. These artifacts help archaeologists build models of what a culture once looked and acted like. And, while certain field sites do, in fact, hold exquisite buildings and stashes of gold coins, most often archaeologists find material remains in more mundane and humble locals, such as in trash pits. It could be said that archaeologists are the ‘trash pandas’ of the anthropology world!

Professor of archaeology, expert on the occult, and how does one say it? Obtainer of rare antiquities.

 Artifacts aid archaeologist to understand human culture. For example, American Southwestern pottery has altered greatly over time, reflecting the skill and technological advancement of the people who have produced it. Additionally, not all southwestern pottery shows the same design, material or color patterns, reflecting cultural differences in how and why the pottery was made and which specific group created it.

Some Famous Archaeologists:

What is a Biological Anthropologist?

I always loved watching the Disney film, Tarzan, as a child. I would dream of being Jane, stomping through a jungle forest and swinging on vines. Lucky enough, as I got older, I actually became a biological anthropologist, which is exactly what Jane and her father were. While I still haven’t found a handsome vine swinging man, I do study primate behavior.

“I am Tarzan of the Apes. I want you. I am yours. You are mine. We live here together always in my house. I will bring you the best of fruits, the tenderest deer, the finest meats that roam the jungle. I will hunt for you. I am the greatest of the jungle fighters.” HUBBA HUBBA Mr. Burroughs

Biological anthropology seeks to understand how the order primates, including humans, have been able to adapt to different environments and why. Observing both living and extinct primates/humans, biological anthropologists compare and contrast anatomy and behavior within the animal kingdom to understand human uniqueness and evolution. While there are many specializations within Biological Anthropology, most can be categorized under two tags- humans and primates. Human specializations in biological anthropology typically study human evolutionary history over the last 5 million years in order to investigate variations in human development and health, to better understand the mechanisms that underlay population differences we see today. Primate specializations in biological anthropology conduct similar studies only rather than looking at one specific species within the order primate, they observe any or all primate species.

Kickass Women Biological Anthropologists:

Who is a Cultural Anthropologist?

It could be said, perhaps, that cultural anthropologists are like the Little Mermaid, Ariel, who wished she could be something or someone else. By observing and collecting the social interactions that people create in their lives, cultural anthropologists aim to explore how people in different locations interact with the world around them. They want to know all aspects of society functions. Why do people think something is important? How and why do people interact with one another? These are some of the many questions cultural anthropologists ask. Cultural anthropologists often agree that the best way to understand the diverse peoples and cultures of our human world is to live among them, known as ethnographic research. In doing so, they attempt to understand the perspectives, practices, and social organization of these groups. So, like Ariel, striving to lose her fish tail and become human, cultural anthropologists, likewise, strive to be “where the people are”.

The IT Crowd Cultural Anthropologists:

To learn more about Anthropology and what it has to offer look no further!

Gobbling Up The Family Tree: Understanding our phylogenetic tree

The primate family tree, also known as a phylogenetic tree, is long and complicated. By observing certain characteristics which an organism has in relation to other organisms, researchers can begin to classify both extinct and extant species into groups (also referred as taxa). This practice of grouping organisms based on shared characteristics is known as taxonomy. Developed by Swedish botanist Carolus Linnaeus in his 1735 book Systema Naturae, Linnaeus used physical characteristics and genetics to identify and differentiate between organisms. Linnaeus created a hierarchy of taxonomic groups to distinguish the amount of similarity between each organism. This hierarchical order can be memorized using a mnemonic device such as “Dear King Phillip Come Over For Good Soup”- Domain, Kingdom, Phylum, Class, Order, Family, Genus, & Species. Linnaeus’s taxonomic system is still used to this day. Each and every organism that you see in the world unless it hasn’t been discovered yet is classified by each of these taxonomic groups.

So, if mom and dad aren’t chimpanzees and grandma isn’t a tarsier, where do we place our human selves on the primate family tree? Biological anthropologists classify primates through varying sets of taxonomic characteristics based on the hierarchical level from Linnaeus’s classification system: kingdom, phylum, class, order, family, genus, species. However, researchers have added more specific taxonomic groups since the establishment of Linnaeus’s taxonomic system. These tend to focus more on the genetic portion of classification, something Linnaeus didn’t really have access to at the time. These groups include semiorders, suborders, infraorders, superfamilies, subfamilies, tribes, subgenera, and subspecies. Both you and all other living and extinct primates appear in one of the many clusters of branches located under the class Mammalia on the phylogenetic tree.

Your fully family tree

Our branch starts at the level of order and expands out all the way to the smallest branches on the tree-subspecies (15&20).  However, belonging to the primate order is quite exclusive. Any organism who wishes to join the order Primates must have the following traits.

Primate Traits

  • Petrosal bulla
  • Intratympanic portions of the facial nerve and carotid circulation
  • Convergent orbits (forward facing eyes)
  • A postorbital bar
  • Flattened nails
  • The ethmoid bone is exposed in the orbit
  • An opposable hallux (thumb & big toe)
  • An anterior elongation of the calcaneus (heel bone)
  • A well-developed groove for the tendon of the flexor digitorum fibularis on the plantar surface of the calcaneal sustentacular process.

With the exception of the petrosal bulla, these features are not found exclusively in primates, however, the combination of these features is (27). Once we’ve passed the primate order, we must then pass the Haplorrhini semiorder, and Anthropoidea suborder. Since Haplorrhines occupy a broader category on the phylogenetic tree (semiorder), the traits or synapomorphies used to classify them will be more numerous than those used to classify Anthropoids, which occupy a narrower category (suborder). Haplorrhini are often diagnosed by soft tissue, dental, and cranial synapomorphies, whereas Anthropoids are often diagnosed by cranial, dental and postcranial synapomorphies.  The synapomorphies for Haplorrhines and Anthropoids are listed below.

Haplorrhine Traits:

  • Soft tissue features include: loss of nasal rhinarium (wet nose), loss of tapetum lucidum, development of a retinal fovea and development of a hemochorial placenta
  • Dental features include: orientation of cristid obliqua and depth of the hypoflexid of the first molar
  • Cranial features include: loss of the ethmoid recess in nasal region and the development of a post-orbital plate
Meet your cousin Jerold, the Tarsier

Anthropoid Traits:

  • Cranial features include: a fused frontal, fused mandibular symphysis, complete postorbital closure, the lacrimal bone located in the orbit
  • Dental feature includes: the posterior-most premolar is always a semimolariform tooth with a differentiated trigonid and talonid
  • Postcranial feature includes: Flattened nail always on the second pedal digit

Following the Anthropoidea suborder, we then pas the Catarrhini infraorder which includes all Old World Monkeys and Apes. Following Catarrhini, we finally reach the branch of the phylogenetic tree closest to our own Hominoidea superfamily (hominoids), which includes all apes: Humans, Gorillas, Chimpanzees, Bonobos, Orangutans and Gibbons (15&31). While Hominoids are less taxonomically diverse than Catarrhines, they do share a common dental formula of 2.1.2.3 and both possess a tubular ectotympanic bone. However, compared to Old World monkeys, hominoids show relatively primitive molar teeth, with rounded cusps. Additionally, hominoids are characterized by broad palates, broad nasal regions, large brains, and no tail. Although Hominoids include all apes, another further division is made to reach us. The Hominidae family only includes the great apes (Gorillas, Orangutan, Chimpanzees, & Bonobos) and humans, allowing researchers to further distinguish differences among primate groups. Passing the Hominidae family branch, we finally arrive at our branch, the Homo genus. While there is only one species currently in the Homo genus, H. sapiens (that’s us!), it also includes all human ancestors. So, while your ancestral family tree might seem long and distant, it’s, in fact, very compact when compared to your phylogenetic primate family tree!

 

 

Who’s That Hominin? The mystery of Homo naledi

Homo sapiens (also known as us!) are currently the only extant species in the genus Homo. But, only 100,000 years ago, many different species of Homo roamed the plant. Paleoanthropologists lump together this collection of different species into one group known as ‘hominins’. Not to be confused with hominids which include primates such as chimpanzees, gorillas, and orangutans, hominins consist exclusively of humans, both modern and extinct from the genera Homo, Australopithecus, Paranthropus and Ardipithecus (1)Homo naledi, first recognized in October of 2013, elicited excitement and controversy within the global paleoanthropological community. Discovered approximately 30 meters (about 98 feet) underground at the Cradle of Humankind World Heritage Site in South Africa, H. naledi was the first of its kind (2). The discovery of H. naledi at an almost impossible to reach location, included at least 1,550 hominin specimens, with 15 individuals exhibiting both Homo and Australopithecus traits, resulting in the upheaval of the already established understanding of our hominin ancestry.

H. naledi was discovered in the Dinaledi Chamber, as a result of speleological surveys throughout the Rising Star Cave system. Accessing the chamber is not an easy feat. In order to reach the Dinaledi Chamber researchers “must be skinny and preferably small…They must not be claustrophobic, they must be fit, they should have some caving experience”- Lee Burger site director. To reach the chamber, researchers must shuffle their way through the cave system’s tight tunnel about 80 meters (260ft) from the entrance to the ante-chamber. Once in the ante-chamber, they must nimbly climb up an exposed vertical face about 15 meters (50ft) to reach a small opening known as the Dragons Back. Researchers must then climb through a narrow, vertically orientated ‘chute’ measuring 12 meters (39ft) long with an average width of 20 cm (7.9in) in order to descend into the Dinaledi Chamber (6). Now that’s a climb! H. naledi is a strange looking hominin. With traits from both the genus Homo and Australopithecus, as well as traits not linked to any other hominin, it’s no wonder that paleoanthropologists were mesmerized by it. And, while there are hominins that exhibit traits from both the genus Homo and Australopithecus, they do not show as confusing morphology as H. naledi. Cranial, lower limb, wrist, and fingertip morphology all are relatively more derived Homo-like traits (2). Whereas brain size, pelvis, fingers, shoulders and ribcage morphology resemble ancestral traits found in Australopithecus more than Homo traits (3 & 4).

H. naledi traits similar to H. erectus

  • thin cranial vault bones becoming thicker in the occipital region
  • presence of temporal and occipital bossing
  • small post-canine teeth
  • vertebrae resemblance
  • homo-like foot and ankle

H. naledi traits similar with Australopithecus

  • Endocranial volume of 465-560 cc
  • Ilia on pelvis is short from top to bottom and flare out broadly side to side (Australopithecus afarensis)
  • Proximal and intermediate phalanges (middle part of your finger) curved
  • Arboreally adapted scapulae (shoulders)
  • Distally wide ribcage

Overall the morphology indicates that H. naledi had an enhanced locomotor performance for a striding (walking) gait, enhanced climbing ability relative to Australopithecus and possible enhanced object manipulation. This strange combination of skeletal and behavioral features contradicts many of the preconceived notions regarding the single evolutionary package in the hominin lineage. This package included an increase in tool manipulation, body size and brain size, smaller dentition, and greater commitment to terrestrial long-distance walking or running (10). So, why does H. naledi not fall under the classical evolutionary package? Well, first of all it is important to note that the H. naledi sample includes many bones that have only been marginally researched in other early hominins (H. rudolfensis, H. habilis and H. erectus). As a result, it can be difficult to determine the amount of morphological similarity between these species (6). Also, the individual mix of primitive and derived characteristics in various Homo fossils may indicate that the genus is polyphyletic, where some members of the genus have originated independently in different regions of Africa (6). If this turns out to be true, it would mean that all species currently placed within the genus Homo would need to be reconsidered. The material, recovered during two different field expeditions (November 2013 and March 2014) to the Dinaledi Chamber, presents a morphologically homogeneous sample that cannot be linked to any other known hominin species (2 & 3). And, while one bird and a few fragmentary rodent remains were discovered alongside the 1,550 hominin specimens, no other faunal evidence has been located. This lack of fauna is unusual and can hold certain implications as to how these hominins arrived in the cave.

There are many different speculations offering explanations of how these hominins arrived in the Dinaledi Chamber, however only two are currently thought to be likely- through a catastrophic event or deliberate disposal. Throughout the hominin record when mono-specific assemblages have been discovered, they are typically associated with a catastrophic event in which a group of animals were trapped. However, this scenario does not explain why these hominins chose to progress so far into the cave system dark zone, and away from all entrance and exit points (7 & 8). The other possible and more controversial scenario is the deliberate disposal of a body. Since none of the fossils to date show any green fractures, or disarticulation, linking to either a fall or predation, some researchers have suggested that H. naledi actively cared for its dead. It has been speculated that since the entrance is quite irregular and narrow, and there is a soft pile of muddy sediment below, bodies could have been dropped down the entrance of the chamber (9). However, this scenario has its flaws, as a long, hard climb through the dark zone is necessary to reach the disposal site, and the intentional disposal of dead bodies is considered a complex behavior for a hominin with a brain no larger than a gorilla, (6 & 9). So, while both of these hypotheses are considered the most plausible compared to others, additional investigation is still required. Aptly put by Mr. Sherlock Holmes “It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts”- A Scandal in Bohemia

These feet are made for walking: Who was Orrorin tugenensis? 

Large and complex brains for our body size, small teeth, and upright walking are some of the characteristics that best define us as individually human.Additionally, our ability to manufacture a wide array of sophisticated tools, engage in complex symbolic and social behaviors, and communicate using spoken language has further distinguished us.

However, many of these characteristics, especially characteristics associated with culture, are not found in association with early hominins.  As a result, researchers must reference the fossil record to help define which specific morphological characteristics have prevailed throughout our lineage. These characteristics can then be applied to any extinct or extant specimen to determine whether it is a Hominini or not. These sets of characteristics become extremely important when observing our earliest ancestors. With the earliest possible human ancestor dated at about 7 million years ago (MYA), and with the split between our chimp cousins and us estimated at the same time, applying these Hominini characteristics help researchers to determine who really was our earliest ancestor.

In 2001, French paleontologist Brigitte Senut and French geologist Martin Pickford discovered Orrorin tugenensis across the Tugen Hills region of central Kenya. Through the use of radioscopic, biochronology and paleomagnetic absolute dating techniques, O. tugenensis, given the name, millennial man, was dated at around 6 to 7 MYA, making it the second oldest possible hominin (Sawada et al. 2012 & Senut et al. 2001). Shalenthropus tchadensis is still the title holder for oldest possible hominin. With at least five individuals, O. tugenensis shows a variety of both hominin and chimp-like traits. When observing the craniofacial functional morphology of O. tugenensis, researchers see a relatively more robust mandible, smaller premolar complex, larger cheek teeth with thin dental enamel, and smaller canines compared to those seen in chimpanzees (Senut et. al 2001). While differences between the dental morphology of chimpanzees and O. tugenensis vary, O. tugenensis morphology still does not directly match up to later hominins. Rather, the dental morphology of O. tugenensis show gradual shifts that start to resemble later hominins such as Ardipithecus ramidus and Kenyanthropus platyopus.   

The Millenium man himself, Orrorin tugenensis!

 When observing the postcranial remains of O. tugenensis, researchers note that the femoral neck is longer than those found in extant apes, suggesting bipedality. Additionally, scans made by computed tomography of the femur show deferential thickness (thicker inferiorly and thinner superiorly) in the cortical bone which is also seen in other hominin bipeds.

However, some of the muscle markings found on the proximal end of the femur could indicate either bipedality or arboreality. Curvature and lengthening of the manual phalanx are also present in O. tugenensis which similarly resembles the finger bones of our more arboreal cousins, the chimpanzees. Furthermore, the humerus also shows a straight lateral crest, where the brachioradialis muscle is able to insert itself (Senut et. al 2001 & Harcourt-Smith 2010). This same feature is seen in both modern chimpanzees and in Au. afarensis and has been linked to climbing adaptations. As a result, postcranially O. tugenensis shows evidence for both bipedalism and arboreal locomotion, creating debates as to how and why it would show adaptations for both.

 We humans are unique among all living primates in the way we move around the earth. So exceedingly rare is our form of locomotion among mammals, that the striding bipedalism we engage in, is, in fact, only noted in one living mammal, us! It is for this reason that bipedalism has become a key indicator in determining whether or not a species is a hominin.

It is a true testament to our evolution that we have the capability of walking in point shoes

With such an unusual form of locomotion, certain specialized anatomical characteristics must be present in order for a body to maintain a committed striding bipedal pattern. In order to walk one foot over the other, the body must be in perfect alignment with its center of gravity. Additionally, since we move one foot at a time, our legs and feet must be fortified to maintain stability. As a result, our bodies have 7 key features which directly aid in balancing and stabilizing the body during bipedal striding. These features include a centrally placed foramen magnum, a sigmoid shaped spine, a shallow and broad shaped pelvis, medially angled femurs, an increased lateral lip on the patella, a robust ankle region (the talus & calcaneus bones) and a non-opposable big toe. The first three features facilitate the body’s ability to support its trunk vertically as well as efficiently transfer weight equally to the legs. The last three features allow for the knee and ankle joints to extend and lock to limit any hyperextension and increase shock absorption and stability (Harcourt-Smith W. 2010).

Anthropologists mainly look for morphology relating to committed bipedal walking (walking on two legs)

One of the central debates concerning hominin evolution is how certain characteristics like bipedalism arose. Many speculate that these features emerged due to changing environments, diet, climate and social dynamics. When observing bipedalism specifically, numerous suggestions have emerged as to what type of locomotion the last common ancestor between humans and chimps had and how different it was to the locomotion patterns we see in both lineages today. Suggestions for the origin of bipedalism include, for example, arboreal bipedalism (Thorp et al. 2007), gibbon-like suspension (Tuttle 1981), terrestrial quadrupedalism and swimming behavior (CITE).

In order to better address the origin of bipedalism, or any behavior for that matter and to help determine possible explanations about early hominins, chimpanzees are often used as a comparative model. This is due to their genetic closeness to humans and to the last common ancestor. However, while using comparative models may be incredibly insightful, researchers must remain vigilant since they may have developed their own suite of divergent traits since the spilt.  Regardless, it is important to remember the complexities of reconstructing any form of behavior on extinct mammals. So, while some evidence points towards bipedality within O. tugenensis, there are still too many unsolved/uncertain variables making some researchers doubt the extent of bipedality within this species.  As a result of this uncertainty, O. tugenensis, like Sahelanthropus, has been classified as a possible hominin. So, while not 100% hominin, O. tugenensis paved the way to the way we walk today!

 

A Long Time ago on a Continent Far Far Away: The Paleolandscape during the Late Miocene

There once was a time when our planet was different from what we see today. It had large lush green forests during the Eocene, and ice covered landscape in the Holocene. And, these climatic and environmental shifts helped to expand, diversify and create new species of organisms, including us. By observing trends in the geological timescale and comparing them to the hominid fossil record, an evolutionary checklist emerges, showing us exactly how and why certain traits were favored over others, and how we as a species came to be.

It is during the Miocene that paleontogists start to recognise more modern fauna and flora.

It is during the Miocene epoch (23.03 to 5.33MYA) that we see the emergence of apes and eventually the earliest hominids. Known as the age of apes, the Miocene shows a rapid radiation of primates across Africa and Eurasia. This expansive diversification of primates, especially apes, has been attributed to the abundance of wet, forested environments. Many of the early Miocene primates such as Victoriapithcus and Paranthropus show adaptations for a more forested environment (5). These traits included longer more curved phalanges, an opposable hallux, muscle attachments indicative of arboreality, and a more inferiorly placed foramen magnum. However, as time moves forward we see the emergence of early hominins (Sahelanthropus & Orrorin) who start to show adaptations to more open habitats, indicating a possible shift in environment. These traits include less curvature of phalanges, a more anteriorly placed foramen magnum, a robust femoral neck and head, and a medial angle positioning of the femur. Additionally, during this time period, the emergence of the African Rift Valley occurs, to which paleoanthropologists and geologists alike attribute climate change and the emergence of hominids.

The African Rift Valley

The African Rift Valley is an extremely large rift or gorge that divides equatorial Africa into Western and Eastern/Southern tip portions. Prior to the full development of the rift valley in the late Miocene, the African continent presented a homogeneous landscape and climate that spanned from the Atlantic to the Indian Ocean. The climate and landscape at that time was warm, wet and overall temperate with forested and woodland regions interlaced with many rivers and lakes. However, at about 8 million years, a large tectonic crisis occurred on the African continent. As the tectonic plates collided with one another, one plate sank causing the valley portion of the African rift, while the rising plate caused the formation of the western mountain ridge surrounding the African rift we see today (3). This new formation disrupted normal air currents causing a gradual shift in climate on the Eastern/ Southern tip of the valley. In the west region, however, the maintenance of regular air currents was upheld. The western air currents were still able to push cooler, wetter air from the Atlantic Ocean, which then formed clouds when mixed with the warmer currents over the continent, resulting in little climatic change.  However, due to the ridge formation on the Eastern portion of the continent, the air currents from the Atlantic was unable to form east of the rift. This resulted in the air and overall climate becoming more arid and seasonal, eventually developing into the Monsoon system we see today. With a gradual increase in aridity, surrounding fauna and flora evolved to match the changing environment. It is assumed that at the time this was all occurring, the common ancestor of both Hominidae and Panidae spanned across the entire continent. Once the African Rift Valley was established, our common ancestor was found on both sides of the valley resulting in the split between Hominidae and Panidae. This would explain why we are genetically similar but removed geographically from our chimp cousins.

Comparative studies at Pennslyvania State College show similar behavioral patterns between a human and chimp infant.

Typically, paleoanthropologists will divide hominid specimens into four separate groups: the possible hominids, the archaic/transitional hominins, the hyper-specialized hominins and early homo. Divisions into these groups are determined by the geological timeline in which the hominid resides and by morphological adaptations exhibited. The first of this grouping, possible hominids, emerge during the Late Miocene and are the first of the hominids. In total, there are three different genera associated with this group: Sahelanthropus, Orrorin, and Ardipithecus. Like most early hominins all three genera exhibit both chimpanzee and hominin traits. However, these genera show the largest amount of chimpanzee traits, making researchers question the exact relationship they have with later hominins (21). Additionally, these Late Miocene fossil remains are, unfortunately, quite limited and fragmented which further complicates researchers’ ability to determine the exact lineage they represent. While these fossils might be few and disjointed, similarities do emerge suggesting to paleoanthropologists that these specimens might be possible humans. As a result, they are loosely attached to the hominin lineage and, thus, called possible hominids.

There are currently two speculations as to why these three genera would exhibit large amounts of primitive/chimp-like traits: 1) the environment during the late Miocene was still a highly riparian, mosaic landscape (rivers bordered by forests, woodlands, etc.), and 2) due to the theorized split of Hominidae and Pangidae species around this time, early hominids would likely exhibit a larger mixture of ancestral and modern traits (21). By using the African Rift Valley as a model, both speculations seem plausible. Throughout the Miocene, the paleolandscape was densely forested and wet (12). However, by the Late Miocene, a gradual shift to a more open and cooler climate occurs. This shift in environment coincides with the emergence of the possible hominins, suggesting a viable connection between ecology and morphology. And, even though the environment was shifting toward becoming more open, there was still a relatively large abundance of forests. This, in combination with how long adaptation occurs, would explain why the possible hominids would have had an abundance of chimp-like traits.