How Homo Sapien morphologies influenced their biological success
Writer: Grace Birkett
Editor: Niru Varma
Artist: Lucie Gourmet
Homo sapiens, or humans, are the most abundant and competent primate in the natural world, and the only extant species of their genus. Their profound interactions with other hominids pose the question of how they alone among the Homos were able to survive, let alone thrive. The Homo genus originated from ape-like hominids known as the Australopithecus. Circa 2 million years ago, Australopithecus experienced several periods of peripatric speciation (https://www.nationalgeographic.org/encyclopedia/speciation/) via natural selection. The varying climates between continents, ranging from taiga biomes scattered across Northern Europe to humid rainforests dispersed throughout Indonesia, gave rise to varying selection pressures and propelled the formation of archaic species, such as Homo neanderthalensis, Homo floresiensis, and ourselves. For example, the demands of Eurasia required a species that possessed a higher muscle mass and a stocky form. As well as this, they developed a peculiar rib cage that removed the presence of a waist, providing sufficient levels of insulation and defining the short and compact torso we have come to associate with H. neanderthalensis. Similarly, the warm African savannahs ultimately shaped the morphology and anatomy of modern humans, as a tall and slender physique allowed us to be more evolutionarily equipped to its conditions. Speciation can also cause great changes in morphology in a short amount of time. Consider H. floresiensis, which underwent a period of mass dwarfism when sea levels rose and restricted islander access to the mainland for nutrients. Consequently, those that required fewer nutrients (the smaller and lighter individuals) were more likely to survive, with most of these individuals clocking in at an astonishing 1 meter tall and a maximum of 25 kilograms.
With each hominid so finely adapted to its niche, what made H. sapiens the most abundant primate, outcompeting other human species, in particular H. neanderthalensis? When they interacted, it became clear that H. sapiens had the upper hand in terms of cognitive function, division of labor, and communication. Neanderthals had greater visual acuity, but it came with the expense of lower language processing abilities. This is in contrast to H. sapiens, who attained biological success from gaining extensive language skills, allowing flexible cooperation in large numbers, and sharing common myths. It could also be possible that different religious beliefs between these hominids resulted in violence, contributing to the eventual downfall of Neanderthals.
Furthermore, Neanderthals’ erroneous division of labor posed a huge disadvantage to their population as their reproductive core, the women and children, would cooperate in hunting large game. This, combined with their tendency to ambush and hunt within a close range to prey, resulted in copious fractures among many Neanderthal skeletons and would’ve most likely participated in their extinction. On the contrary, H. Sapiens’ division of labor was composed of males who would violently hunt large prey and females who would participate in gathering smaller foods and bear children. Additionally, differences in pelvic anatomy show that Neanderthals’ center of gravity passes vertically through the hip joints and the legs. Modern humans have a center of gravity in zigzag configuration, creating a cantilevered, shock-absorbing body structure that enhances propulsion during movement . Such pelvic anatomy aided H. sapiens when hunting and fleeing from predators. Other features, such as the domestication of the dog, may have added benefits when hunting. Evidence for this was found in the Razboinichya Cave (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3145761/) located in the Altai Mountains, where morphological criteria were used to identify a canid skull. The creature was more similar to a domesticated dog from Greenland than a wolf. In one layer of the cave were small charcoal pieces and burnt bones, signs that hominids, perhaps H. sapiens, visited the cave at least occasionally.
Features such as an enhanced division of labor, finer pelvic anatomy and visual acuity ultimately enabled modern humans to exploit their environment, cultivate the land, develop trade, create art, and even study life. Studies into the history of our evolution and the processes that drive it can be applied to sustain not just our species, but the great diversity of species that surround us too.