That our ancestors were adept at climbing trees is widely proven by science: just like our closest ape relatives, such as chimpanzees, gorillas, and orangutans, the ancestors of man used the branches as a shelter or place in the have to find sustenance. However, the question that alludes to when we get off of them to start walk on our two legs, a trait that clearly identifies us as humans, is an unknown that still lasts. Even if there was a time when we combine life on the ground with regular crossings between branches. A new study led by the Kent University He claims to have found evidence that this important transition was not as abrupt as previously thought.
Research indicates that some of our hominid ancestors routinely combined both environments just between one and three million years ago, as reflected in the study published in the journal « Proceedings of the National Academy of Sciences»(PNAS). This new research, based on fossil leg bone analysis, provides evidence that at least one species of hominid (it is not clear if the Paranthropus robustus or is it a Homo early, since both they coincided in space and time) regularly adopted highly flexed hip joints, a posture associated with tree climbing by other apes.
“While we know that all human ancestors practiced some form of walking -they walked on his two feet-, it is not clear when (and what) human ancestors they walked from the same way as modern humans“Say the researchers. “There is increasing evidence that these ancestors walked on their two legs in a different way than ours, and many fossils still display ape features, especially in their upper limbs. Therefore, there has been a long debate about the importance of climbing (tree locomotion) in our evolutionary history, and whether our ancestors were focused on walking on the ground alone or whether trees were still an important part of their lifestyle. ».
In search of the inner secret of the bones
The team analyzed and compared the internal bone structures of two leg bones found in the Sterkfontein cave, in South Africa, on an expedition about 60 years ago. Dating places these remains between 1 and 3 million years ago and it is known that both were bipeds. Externally, in both cases, a joint more human-like than ape-like was shown, suggesting that these ancient hominids did indeed walk on both legs. However, by analyzing the interior of the head of the femur with high-resolution microtomography (microCT) techniques – which is similar to computed tomography, but with higher resolution – the team realized that the hip joints they carried more similarly to that of primates that climb trees.
“It has been a challenge to find a solution to the debates about how exactly our ancestors walked bipeds and whether they still climbed trees because the external shape of the bones can be misleading. In particular, it is not clear whether the ape features in some hominin fossils were still functionally useful, or if they were simply reminiscent of a more arboreal ancestor that had not yet been lost (because behavior can evolve faster than morphology), “the researchers explain.
When we start walking on two legs
It is known that first human ancestors they started to walk on both legs they did it between 4 and 7 million years, although they carried out this practice in a occasional, the trees being their natural environment. The general consensus was that it was approximately 2 million years when our relatives, both Paranthropus and the first Homo, began to make life on the ground on a regular basis, moving to sporadic climbing.
But the evidence has been scant, controversial, and not widely accepted. Our results provide direct evidence that members of one of these species regularly adopted highly flexed hip joints, a posture that in other non-human apes is associated with tree climbing, “they state. That is, we walk on the ground as much as we climb trees.
In addition to the evidence that these specimens lived on land and in “air,” the research leaders, Leoni Georgiou, Matthew Skinner Y Tracy Kivell, from the University of Kent School of Anthropology and Conservation, stress that this technique can shed light on secrets that still exist within fossil bones, which can literally alter or even revolutionize what we think we know about our ancestors.
“It is very exciting to be able to reconstruct the actual behavior of these people who lived millions of years ago, and every time we explore a new fossil with this new technology, it is an opportunity to learn something new about our evolutionary history,” says Georgiou. For his part, Skinner points out: “It has been a challenge to resolve debates about the degree to which climbing continued to be an important behavior in our past. Further analysis of the internal structure of other skeletal bones may reveal interesting findings about the evolution of other key human behaviors, such as stone tool making and the Tools use. Our research team is now expanding our work to look at the hands, feet, knees, shoulders, and spine. ”