What we discovered about ancient human origins this year… and what is still a mystery
This year, huge strides were made in unravelling some of the mysteries of our ancient ancestors. For example, in the first ever analysis of a virtually complete Neanderthal genome, scientists were able to prove that rampant interbreeding occurred between Humans, Neanderthals and other species, resulting in an incredibly complex family tree. However, other studies revealed that there is so much more about our ancestry that we still don’t know, such as several studies pointing to the possibility of a completely unknown ancient human lineage. Here is a snap shot of some of the most significant studies to be made in 2013 relating to our ancient human origins.
What was revealed about Inter-breeding and how it formed our family tree
It was long believed that Neanderthals became extinct before modern Humans even emerged. However, this theory was later revised and it became accepted that Neanderthals and modern Humans had a cross-over of thousands of years, but never encountered each other. New evidence caused a revision yet again, this time saying that Neanderthals and modern Humans did indeed encounter each other but never interbred. And this year, in yet another shake-up of old theories, a number of studies have presented evidence that Humans and Neanderthals did interbreed and produce offspring.
In one of the most dramatic studies that have been seen in many years, scientists were able to extract DNA from a 50,000-year-old fossil that came from a Neanderthal woman found in a Siberian cave and piece together the Neanderthal genome to the same level of detail that has been achieved in modern day humans. The results showed that ancient human species, including Neanderthals, Denisovans and Homo sapiens mated with each other, resulting in an incredibly complex family tree. In fact, it was found that about 1.5 to 2.1 percent of the DNA of people with European ancestry can be traced to Neanderthals; proportions of Neanderthal DNA are higher among Asians and Native Americans, who also have small percentages of Denisovan DNA; six percent of the genome of Australian Aborigines and indigenous Papua New Guineans belong to the Denisovan species; and only 96 genes responsible for making proteins in cells are different between modern humans and Neanderthals.
This supports a unique finding made in a rock shelter in Lisbon, Portugal some years ago, in which archaeologists uncovered the bones of a four-year-old child, comprising the first complete Palaeolithic skeleton ever dug in Iberia. The significance of the discovery was that an analysis of the bones revealed that the child, who became known as ‘ the Lapedo Child’ , had the chin and lower arms of a human, but the jaw and build of a Neanderthal, suggesting that he was a hybrid, the result of interbreeding between the two species.
However, the study on the fossil found in the Siberian cave produced another totally unexpected finding – the Denisovans share up to 8 percent of their genome with a “super archaic” and totally unknown species that dates back around 1 million years. It appears that the Denisovans bred with a mystery species from Asia – one that is neither human nor Neanderthal. Traces of the unknown new genome were detected in two teeth and a finger bone of a Denisovan. In fact, there have been several studies this year which have all pointed to the fact that there is unknown species in our family tree that is yet to be identified.
A mysterious unknown lineage
A landmark study this year revealed the oldest known human DNA ever to be found, dating back approximately 400,000 years – substantially older than the previous earliest human DNA from a 100,000-year-old Neanderthal. It came from a hominin found in Sima de los Huesos, the “bone pit”, which is a cave site in Northern Spain. Initial analysis on the DNA revealed a complex and confusing interbreeding of species which took place in our ancient past. The scientists were able to use novel techniques to extract the DNA and determined an almost complete mitochondrial genome sequence of a 400,000-year-old representative of the Homo genus. The researchers then compared the DNA with Neanderthals, Denisovans, and present-day humans, and found that the individual shared a common ancestor with the Denisovans, a relatively newfound relative of humans who are thought to have lived in the vast expanse from Siberia to Southeast Asia. This was unexpected since the skeletal remains carry Neanderthal-derived features. In addition, the fossil was uncovered in Europe and not eastern Asia where it was believed the Denisovans lived. The investigators suggested that a currently unknown species brought Denisovan-like DNA into the Pit of Bones region, and possibly also to the Denisovans in Asia.