Fossil apes can tell us about essential aspects of the evolution of apes and humans, including the nature of our last common ancestor.
In the 150 years since Charles Darwin assumed humans were from Africa, the number of species in the human family tree has exploded, as has the level of controversy regarding early human evolution. Fossil apes are often at the center of the debate, with some scientists dismissing their importance in the origins of human lineage (the “hominins”), and others giving them evolutionary roles. A new review published on May 7 in the review Science examines the main discoveries about the origins of hominids since Darwin’s work and argues that fossil apes can inform us about essential aspects of the evolution of apes and humans, including the nature of our last common ancestor.
Humans diverged from apes – in particular, the chimpanzee lineage – at some point between about 9.3 million and 6.5 million years ago, towards the end of the Miocene era. To understand the origins of hominids, paleoanthropologists aim to piece together the physical characteristics, behavior, and environment of the last common ancestor of humans and chimpanzees.
“When you look at the story of the origins of hominids, it’s just a big mess – there’s no consensus,” said Sergio Almécija, senior researcher in the Anthropology Division of the American Museum of Natural History and author principal of the journal. “People work under completely different paradigms, and that’s something I don’t see happening in other areas of science.”
There are two major approaches to solving the problem of human origins: “Top-down”, which is based on the analysis of living monkeys, in particular chimpanzees; and “from the bottom up,” which places importance on the largest tree of the mostly extinct great apes. For example, some scientists speculate that hominids originated from an ancestor who stepped on the joints of the chimpanzee. Others argue that the human line originated from an ancestor more resembling, in some characteristics, some of the strange Miocene apes.
Examining the studies surrounding these divergent approaches, Almécija and colleagues with expertise ranging from paleontology to functional morphology and phylogenetics discuss the limitations of relying exclusively on one of these opposing approaches to the problem of hominid origins. . “Top-down” studies sometimes ignore the reality that living apes (humans, chimpanzees, gorillas, orangutans, and hylobatids) are only the survivors of a much larger group, and now mostly extinct. On the other hand, studies based on the “bottom-up” approach tend to give individual fossil apes an important evolutionary role that corresponds to a pre-existing narrative.
“In The Descent of Man in 1871, Darwin hypothesized that humans originated in Africa from an ancestor different from any living species. However, he remained cautious given the scarcity of fossils at the time, ”Almécija said. “One hundred and fifty years later, possible hominids – approaching the time of the human-chimpanzee divergence – have been found in East and Central Africa, and some even claim in Europe. In addition, more than 50 genera of fossil monkeys are now documented in Africa and Eurasia. However, many of these fossils exhibit combinations of mosaic features that do not meet the expectations of ancient representatives of modern lineages of monkeys and humans. As a result, there is no scientific consensus on the evolutionary role played by these fossil apes. “
Overall, researchers have found that most human-made stories are incompatible with the fossils we have today.
“Living monkey species are specialized species, relics of a much larger group of now extinct apes. When we consider all of the evidence – i.e. living and fossil apes and hominids – it is clear that a human evolutionary story based on the few species of apes currently living is missing much of the evidence. the big picture, ”said Ashley Hammond, study co-author, assistant curator in the Museum’s Anthropology Division.
Kelsey Pugh, Museum postdoctoral fellow and study co-author, adds: “The unique and sometimes unexpected characteristics and combinations of characteristics observed in fossil apes, which often differ from those of living apes, are necessary to unravel the characteristics. hominids inherited from our monkey. ancestors and who are unique to our lineage.
Monkeys living alone, the authors conclude, offer insufficient evidence. “The current disparate theories regarding apes and human evolution would be much more informed if, along with the earliest hominids and living apes, Miocene apes were also included in the equation,” says Almécija. “In other words, fossil apes are essential in reconstructing the ‘starting point’ from which humans and chimpanzees evolved.”
Reference: “Fossil apes and human evolution” by Sergio Almécija, Ashley S. Hammond, Nathan E. Thompson, Kelsey D. Pugh, Salvador Moyà-Solà and David M. Alba, May 7, 2021, Science.
DOI: 10.1126 / science.abb4363