Top 10 Human Origins Discoveries in 2015
A study of skull fragments and teeth discovered in 1976 in a cave in Xujiayoa, China suggests that there may well have been multiple species of primitive humans between 60,000 and 120,000 years ago – including a mysterious people who do not fall under the categories of either Neanderthals, Denisovans, or modern humans.
Dental remains were recovered from the fragments that identify to four individuals. These were examined for size, shape and surface of the teeth, as well as other defining characteristics. When the teeth were compared to a database of over 5,000 teeth of known species, they did not match any of the accepted hominids. The question is now whether the teeth represent a hybrid of Denisovans and modern humans, or whether scientists have an entirely new human species on their hands.
In May last year, archaeologists made the exciting announcement that a complete Ice Age skeleton had been found in an underwater cave in Tulum, Mexico. Since then, more than eight well-preserved skeletons, ranging in age from 9,000 to 13,000 years have been retrieved from cenotes in Mexico and now scientists have begun to unravel the secrets that they may hold about early migration in the Americas.
The differences in skull shapes between the current indigenous people of Mexico and the Ice Age samples led some experts to argue that Native Americans arrived in a later migration to the earliest inhabitants, who came from elsewhere. According to this theory, the first wave of people was an Asian group that arrived more than 15,000 years ago via the Bering Strait, at the easternmost tip of Siberia and Alaska (the Paleoamericans), while a second migration wave occurred around 8,000 – 9,000 years ago and are the ancestors of today’s Native Americans. However, until further evidence emerges, it cannot yet be determined whether the differences in skull features between Paleoamericans and later Native Americans is accounted for by evolution or by two distinct migrations.
DNA from fossils from the Sima de los Huesos (“pit of bones”) cave in Spain show that Neanderthals are almost twice as old as previously thought, having emerged up to 765,000 years ago.
The scientists sequenced DNA from a prehistoric tooth and a leg bone, dating them to between 300,000 and 400,000 years old. They also identified one million to two million base pairs of ancient nuclear DNA, which is the oldest partial genome ever sequenced.
The findings “could lead to a dramatic shake up of the current shape of the human family tree,” as it was previously believed that Homo sapiens (modern humans) only emerged in Africa 200,000 years ago before they spread across the world. Neanderthals were believed to have evolved in Eurasia from a common ancestor. The new genome results create an earlier timeline for both species, and thus an earlier split in the evolutionary tree.
A study published in August asserts that modern humans lost DNA as we evolved after our split from apes. Our ancient ancestors, early humans, possessed substantially more amounts of genetic data than we do now. This surprising discovery raises many questions, the most obvious one being: why did we lose all that genetic information? Also, what difference has the loss made? The short answer is: we don’t know yet. This is the first time scientists have documented the loss (and gain) of large chunks of DNA in ancient populations.
The geneticists sequenced the genomes of 236 individuals from 125 distinct populations. They found that Homo sapiens have shed approximately 40.7 million base pairs of DNA after breaking from our closest living relatives, chimpanzees, around 13 million years ago. Furthermore, at least 27.96 million of the base pairs lost were unique.
Scientists also announced an earlier time frame than previously estimated for the lifetime of an early proto-human dubbed Little Foot – as much as 3.67 million years ago. The nearly complete fossilized skeleton of the small Australopithecus creature was found in Sterkfontein Cave in South Africa in the 1990s.
Age estimates of the fossil have varied greatly over the years, but new dating methods have allowed a more precise estimate. ‘It was impossible to fit Little Foot into the human family tree with any certainty because “ever since its discovery, the age of Little Foot has been debated,” said lead study author Darryl Granger, a geochronologist at Purdue University in West Lafayette, Indiana. ‘If researchers can figure out when Little Foot arose, they might be able to better pinpoint which Australopithecus species and which part of Africa ultimately gave rise to Homo.’