Australopithecus afarensis was one of the longest-lived and best-known early human species.The species, whose most famous fossil ‘Lucy’ comes from Ethiopia, roamed the Earth around 3.2 million years ago – and new evidence has found they were not alone.
Four different species of hominin co-existed at the time of Lucy, according to the results of an in-depth review of the fossil evidence gathered over the last few years.
Australopithecus afarensis was one of the longest-lived and best known early human species.The species, whose most famous fossil ‘Lucy’ comes from Ethiopia, roamed the Earth around 3.2 million years ago – but recent evidence has suggested they were not alone.
The discovery of a 3.4 million-year-old Burtele partial foot announced in 2012 was the first conclusive evidence that another early human ancestor species lived alongside Australopithecus afarensis.
This species was identified as Australopithecus deyiremeda, a 3.5 to 3.3 million-year-old human ancestor species from Ethiopia, named in 2015.
This finding proves more than one separate human species existed around 3 million years ago, an idea that was not widely accepted for a long time.
The review concluded that four different species of potential human ancestors lived at that time.The review was published in the Proceedings of the National Academy of Sciences. Also, new analysis suggests Neanderthal DNA may hold hidden clues as to why they shuffled of the evolutionary stage, and may have left modern humans genetically weaker.
Researchers believe that as their numbers dwindled, inbreeding would have led to a build-up of genetic mutations which made our extinct cousins unable to reproduce as effectively – a genetic legacy which non-African people still carry with them today.Genetic analysis has revealed that mutations built up in Neanderthal DNA over time, due to inbreeding.
The findings are published in the journal Genetics. The accumulation of genetic errors meant their ability to have children was reduced by up to 40 per cent. This may reduce reproductive fitness of non-African people today by one per cent. Indigenous sub-Saharan Africans have been found to have no Neanderthal DNA, as their ancestors did not follow the same migration route.
Scientists have been able to glean a lot of information on the fate of Neanderthals from genetic analysis of humans alive today, with estimates that people may be able to trace anywhere from two to four per cent of their DNA to Neanderthals.
But when the two species shared the Earth at the same time between 50,000 to 100,000 years ago, interbreeding meant this figure was likely closer to 10 per cent.
Lead author and curator of physical anthropology at The Cleveland Museum of Natural History, United States, Dr. Yohannes Haile-Selassie, said: “It is now obvious that more than one species of early hominin co-existed during Lucy’s time.
Until 1995, the fossil record suggested there was only one pre-human species at any given time before three million years ago. It was thought each species gave rise to another new species through time in a linear manner.
But the discovery of Australopithecus bahrelghazali from Chad in 1995 and Kenyanthropus platyops from Kenya in 2001 challenged this idea.
These two species were not widely accepted, and instead considered as geographic variants of Lucy’s species, Australopithecus afarensis.
The discovery of a 3.4 million-year-old Burtele partial foot from the Woranso-Mille announced by Haile-Selassie in 2012 was the first conclusive evidence that another early human ancestor species lived alongside Australopithecus afarensis.
Meanwhile, a geneticist at Stanford University, United States, Dr. Kelley Harris, who led the Neanderthals research said: “Neanderthals are fascinating to geneticists because they provide an opportunity to study what happens when two groups of humans evolve independently for a long time—and then come back together…”
“Our results suggest that inheriting Neanderthal DNA came at a cost.”Analysing the genetic remnants carried by humans today, the team found stretches of Neanderthal DNA are concentrated in certain regions of the human genome – indicating mutations have likely been weeded out from other regions over time.
The researchers believe the erroneous code would have resulted in mild, but harmful genetic effects for the carrier.Previous studies of Neanderthal remains have revealed that the ancient hominids were far less numerous and less diverse than humans.
While such faulty code would have been slowly weeded out in humans over time, in the far smaller Neanderthal populations they would have been passed back and forth.
Over time, this build-up of mutations could have made Neanderthals up to 40 per cent less reproductively fit as the humans which had flooded Europe and Asia from Africa.
The team combined this information in computer simulations, based on the proportion of Neanderthal DNA, how often mutations would arise and population dynamics.
Indigenous sub-Saharan Africans have been found to have no Neanderthal DNA, as their ancestors did not follow the same migration route.A series of recent discoveries are revealing Neanderthals in new light, suggesting they were skilled toolmakers with adept hand eye coordination and a well developed culture.
A recent study, published in the journal Nature, suggests that 176,000 years ago, Neanderthals were already constructing stone structures in a cave in south west France.
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