opinion
By Meskerem Lemma
… the other, the southern route, brought humans through what is now Ethiopia and Arabia.
Lucy, also known as ‘Dinkinesh’ in local language Amharic to say ‘you are rattling’, is a collection of several pieces of bone representing about 40 per cent of the skeleton of a female Australopithecus Afarensis. It was discovered in 1974 at Hadar in the Awash valley of the Afar. In paleoanthropology usually only fossil fragments are found and only rarely are skulls or ribs uncovered intact; thus this discovery was extraordinary and provided an enormous amount of scientific evidence. Lucy is estimated to have lived 3.2 million years ago, and is classified as a hominin.
Nevertheless, one of the most important periods in human evolution–the origins of our lineage–has long been least understood. But thanks to a fossil find adds another twig to the human evolutionary tree, giving further evidence that the well-known “Lucy” species had company in what is now Ethiopia a new study says.
The discovery of this fossil evidence, which consists a lower jaw, plus jaw fragments and teeth, dated at 3.3 million to 3.5 million years old, were found in the Afar state of northern Ethiopia four years ago. The discovery suggests that our family tree has more branches than previously believed and is far from linear. The age of the remains indicates that up to four different species of early humans might have been alive at the same time — challenging a long-held belief that there was only one pre-human species at any given time between 3 mln and 4 mln years ago.
The fossils were discovered less than 22 miles from where Lucy is believed to have lived. The researchers, in a paper released on 27 May 2015, by the journal Nature, announced the new finding and assign it to a species they dubbed deyiremeda. In the Afar language the second name means “close relative,” referring to its apparent relationship to later members of the evolutionary tree.
But nobody knows just how it’s related to our own branch of the family tree, said, Yohannes Haile-Selassie — a curator of physical anthropology at the U.S. museum,who led the international team of scientists that made the discovery.
“This new species from Ethiopia takes the ongoing debate on early hominin diversity to another level,” Haile-Selassie said in the statement. “Some of our colleagues are going to be skeptical about this new species, which is not unusual. However, I think it is time that we look into the earlier phases of our evolution with an open mind and carefully examine the currently available fossil evidence.”
“The new species is the most conclusive evidence for the contemporaneous presence of more than one closely related early human ancestor species prior to 3 million years ago,” the Cleveland Museum of Natural History also said in a statement released last Wednesday.
Our branch, which includes Homo Sapiens and our closest extinct relatives, arose from the evolutionary grouping that now includes the new creature as well as Lucy’s species. The new arrival, and the possibility of still more to come, complicates the question of which species led to our branch, he said.
Previously, fossilized foot bones found in 2009 near the new discovery site had indicated the presence of a second species. But those bones were not assigned to any species, and it’s not clear whether they belong to the newly identified species either, Haile-Selassie said.
Bernard Wood of George Washington University, who didn’t participate in the new work, said the discovery provides “compelling evidence” that a second creature lived in the vicinity of Lucy’s species at the same time. The next question, he said, is how they shared the landscape? “These fossils certainly create an agenda for a lot of interesting research that’s going to be done in the next decade,” Wood said.
As evidence that the new fossils represent a previously unknown species, the researchers cite specific anatomical differences with known fossils. But Tim White, a University of California, Berkeley, expert in human evolution, was unimpressed. He said he thinks the fossils actually come from Lucy’s species “Anatomical variation within a biological species is normal,” he said in an email. “That’s why so many announcements of this sort are quickly overturned.”
These fossils certainly create an agenda for a lot of interesting research that’s going to be done in the next decade. On the other hand, a new genetic analysis suggests the major gateway for modern humans out of Africa may have been Egypt. This finding may help scientists reconstruct how humans evolved as they wandered across the globe, according to the researchers. Previous research suggested the exodus from Africa started between 70,000 and 40,000 years ago.
The recent study published in the American Journal of Human Genetics, the scientists detailed their findings on 28 May 2015, hinted that modern humans might have begun their march across the globe as early as 130,000 years ago, and continued their expansion out of Africa in multiple waves. When and how the modern human lineage crossed the Sahara and dispersed from Africa has long been controversial.
Scientists had suggested two routes for the exodus from Africa. One, known as the northern route, has humans outflowing through what is now Egypt and Sinai. The other, the southern route, brought humans through what is now Ethiopia and Arabia. The available evidence for either migratory path remains inconclusive.
To see which route the ancestors of all humans outside of Africa might have taken, the researchers sequenced the genomes of 225 people from northeast Africa — 100 Egyptians and 125 Ethiopians. They then compared this data with DNA from East Asians, South Asians and Europeans — specifically, Han Chinese, Gujarati Indians and Tuscan Italians, respectively. They also compared this data with DNA from modern West Africans from south of the Sahara, which should generally reflect the ancient sub-Saharan gene pool.
The scientists noted that both modern Egyptians and Ethiopians have recently experienced migrations from outside Africa, and the interbreeding that resulted might increase their genetic similarity with those migratory people. To account for this, the researchers removed any genetic sequences that might have come from these recent migrations.
If the southern route was the main path out of Africa, Ethiopians should be more genetically similar to Eurasians. Instead, the researchers found that Egyptians were more genetically similar to Eurasians, suggesting the northern route was the predominant way out of Africa. The researchers estimated that Eurasians genetically diverged from Egyptians 55,000 years ago, Ethiopians 65,000 years ago and West Africans 75,000 years ago.
“The most exciting consequence of our results is to have unveiled an episode of the evolutionary past of all Eurasians, therefore potentially improving the knowledge of billions of people on their deep biological history,”study lead author Luca Pagani, a molecular anthropologist at the Welcome Trust Sanger Institute and the University of Cambridge in England, told Live Science.
The northern route as the preferred way from Africa is supported by the fact that all non-Africans possess DNA form Neanderthals, who were present along the northern route in the eastern Mediterranean at the time. This new finding is also in agreement with the recent discovery of modern human fossils in Israel close to the northern route that date to about 55,000 years ago.
Although there is genetic and archaeological evidence that some people did take the southern route out of Africa, perhaps those people got no farther than Arabia, or left no genetic trace in modern Eurasians. In the future, scientists could investigate whether anyone who took the southern route left any genetic traces in modern Oceanians, Pagani said.