After writing about Religion, and Passion & Success, and nearing the end of the year, I decided to return back to my older interests on evolution, especially the Human evolution.
Many of us would have heard about Neanderthals, our (Homo sapiens sapiens) closest relatives. Neanderthals (Homo sapiens neanderthalensis) have become extinct from this earth, 28,000 years ago. They were said to be ruling this earth for more than 200,000 years, especially in regions of today's Europe and Western Asia. They lived in regions around today's Israel, Mongolia, Italy, Gibraltar, and Britain, but gradually moved from place to place.
Research shows that modern humans (Homo sapiens sapiens) invaded Europe, starting a little more than 40,000 years ago which means that Neanderthals and our current species would have lived together in the same region or territory for a period of 12,000 - 15,000 years. This makes it interesting. The Neanderthals and modern humans probably lived most of their lives without seeing each other; or rather kept away from each other from the landscape.
The last batch of Neanderthals are believed to have lived in the now British territory of Gibraltar, some 28,000 years ago. The prime reasons being cited for extinction of Neanderthals are Climate Change and subtle differences in their behavior and biology. It is known that Neanderthals were bigger in size than Homo sapiens sapiens, and therefore would have required 4034 Calories per day, while a modern human being required only 2200 calories per day, which might have caused the Neanderthals to hunt for bigger animals only (like horses, deer, bison and Wild cattle etc..), though they ate vegetables and other plant food, they served only as supplementary food items for them.
Humans on the other hand might have hunted for smaller animals, survived with plants and vegetables (latter activities were primarily carried out by women), during the extreme climatic conditions that were changing rapidly within a span of few decades. Therefore humans survived with diversified diet. Another theory is that, Neanderthals had different cognitive capabilities than modern humans; as they reproduced 4 years earlier than in modern humans and therefore matured earlier.
Now the developing story of our history is about the discovery of a new Denisovans - another sub-species of Homo sapiens, who seem to have coexisted in Asia with Neanderthals and early modern humans. To begin with, the common ancestor of modern humans, Neanderthals and Denisovans would be Homo heidelbergensis, (though some scientists consider it an European species ancestral to neanderthals alone) who existed 700,000 years ago and began to diverge into these two groups and so far. But now a discovery in the Caves of Siberia, called the Denisova Cave, a new human species - Denisovans seem to have existed 190,000 years ago. The surprising and interesting thing is that, this cave seems to have been home for both Neanderthals and Denisovans.
Denisovans are closer to Neanderthals in their DNA and reveals that both might have interbreed with each other. However it is highly likely that Denisovans might have interbreed with another species (yet-to-be identified) which would have created them. The DNA analysis also tells that traces of Neanderthal DNA (approx 2.5%) in found all non-Africans today and of Denisovan DNA (5%) found in today's Melanesians - the aboriginal Australasians. It may be noted that African populations do not have Neanderthal or Denisovan ancestry because those species were never on that continent. This means that humans (Homo sapiens sapiens) interbreed with both Neanderthals and Denisovans and also provide strength to the argument that Neanderthals were with the West, and Denisovans with the East.
Prior to this, the discovery of the remains of Homo sapiens idaltu, another extinct sub-species of us, was found in Ethiopia in 2003. This species is argued as the ancestors for us - Homo sapiens sapiens. The discovery of yet another species - Homo floresiensis - known as Hobbit (as they were known to be very short) through the remains found in Indonesia in 2004 tells about another human species that is considered to be from Homo erectus, another of our sibling that would have lived with the modern humans for a long time.
Prior to this, the discovery of the remains of Homo sapiens idaltu, another extinct sub-species of us, was found in Ethiopia in 2003. This species is argued as the ancestors for us - Homo sapiens sapiens. The discovery of yet another species - Homo floresiensis - known as Hobbit (as they were known to be very short) through the remains found in Indonesia in 2004 tells about another human species that is considered to be from Homo erectus, another of our sibling that would have lived with the modern humans for a long time.
Well, the story does not end here, and hopefully, even more mysteries of our species will be unraveled in future.
Sources of Info:
- National Geographic , October, 2008
- Scientific American, August 2009
- Scientific American, August 2012
- National Geographic, July 2013
- New Scientist, November 2013
Update - March 2016:
A DNA sequencing study of Melanesians (people on the equatorial islands of Melanesia) having appreciable levels (2 - 4%) of Denisovan ancestry also had 1.5% to 4% of Neanderthal genetic ancestry. This indicates that at least 4 species of hominins (our species - Homo Sapiens, Neanderthals, Denisovans, and yet-to-be discovered another extinct human species) were alive at the same time and were interbreeding at times over the last 100,000 years.
