The World Before Us: How Science is Revealing a New Story of Our Human Origins

Tom Higham is Professor of Archaeological Science at the University of Oxford and Director of the Oxford Radiocarbon Accelerator Unit. He was part of the team that found and identified a previously unknown hominin – the Denisovans – named after the Denisova Cave in Siberia where the first remains were found. A further discovery was a first-generation offspring of two different types of hominin, a Neanderthal and a Denisovan. This hybrid was identified by DNA testing in 2010 from a piece of her finger bone discovered in 2008.

Finding an ancient bone that turned out to be a hybrid of a Neanderthal mother and Denisovan father was the greatest day in the career of everyone working on the project. Higham describes his reaction:

    “I wish I had a video of the moment I was told this news; I think my jaw must have dropped open as I sat stunned and wide-eyed. We all were. I was thinking, how could this be? There must be a mistake, a mix-up, some kind of contamination or other error. Later, the extracts were done again and again to make sure. Same result each time. It was an incredible thing to comprehend. We told Sam the ‘secret’ news, that she may have found a hybrid – not a Neanderthal, but something part-Denisovan after all!”

This discovery was possible because of very recent techniques of DNA sequencing that were developed at the Department of Genetics at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. These techniques are described in this book, and even more fully in the book Neanderthal Man: In Search of Lost Genomes by Svante Pääbo (see my post of 22 March).

Higham describes other recently identified hominins, including a new type of human that was discovered in 2004 in a cave on the island of Flores in Indonesia. It has been named Homo floresiensis, but because of its small size (an adult being no more than 1 meter tall), it is known as ‘the Hobbit.’

Of this incredible discovery, Higham writes:

    “Certainly, it brought us closer to confirmation that the earth was richer in human diversity than had been previously thought. Indeed, the discoveries of new human groups are still happening, the latest as recently as January 2019, and we now know there were at least five different groups of humans living at broadly the same time 40-120,000 years ago, and probably for several tens of thousands of years before that. The 2004 discovery sparked an increased and continuing level of interest in the islands of Southeast Asia.”

Higham gives detailed information about how each of these new hominins were found, and the latest science advances that enabled their identification. One technique in particular seems unbelievable – being able to extract DNA from soil. In places where there is evidence of human habitation, archaeologists are now able to test the surrounding soil for traces of the animals and humans that lived there.

    “It seems that we don’t even need bones now to do archaeology; just sediment will do in some cases. It is incredible but true to say that if we had never found any physical remains of Denisovans, no bones or teeth, we would still know about them now from the sediment DNA work alone. It’s a truly remarkable feat of science that we can do this work.”

And, “Who knows what other, as yet unidentified hominins, might be lurking in the dirt?”

Finding evidence of Homo sapiens in the same areas has also given archaeologists and anthropologists updated information about where our ancestors lived and how and when they migrated.

Higham ends the book by stating:

    “We have learnt much in the last decade, but there remains so much more to find out and many questions that are as yet unanswered. With new excavations and the application of more cutting-edge science, we will surely obtain many more insights into Denisovans, Neanderthals, Hobbits, Homo luzonensis, Homo erectus and perhaps other human groups yet to be discovered. If the last decade is anything to go by, we are in for an exciting ride.”

I’m looking forward to reading and learning more about that ride!