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).
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.
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.