Since I was a teenager I have been interested in the topic of origins; the origin of humankind, life on Earth, the planets, the solar system and the cosmos. No, I am definitely not suggesting that I possess all the answers to these questions. No single individual can make such a claim. My late father had books on these topics, in particular human evolution, on the bookshelves. I read as many of them as I could.

Times have changed since I was in school, pouring over biology and geology texts, examining pictures of Richard Leakey holding hominin fossil skulls in his hands. Fossils are crucial, to be sure, but they are not the only way to uncover previously unknown hominin species.

When it comes to the origins and evolution of Homo sapiens, no other subject – with the possible exception of cosmology – has changed so much in the last fifty years.

Discoveries of extinct hominin fossils have changed our simplistic picture of human evolution. The linear model of from ape to human is not only wrong, but outdated. We are all familiar with the wonderful discovery of Lucy in 1974. But that is only one part of an increasingly complex, multifaceted picture.

Ancient DNA and modern humans

The impact of genetics – specifically ancient DNA – on the field of human origins cannot be overestimated. The dizzying array of discoveries of ancient hominins have revealed a complex picture; not only did Homo sapiens coexist with other, now-extinct hominins, they interbred with them.

Jordana Cepelewicz, writing in Quanta magazine in 2019, makes an astute observation. With the advent of ancient DNA, and the analysis of their contents, reveals that Homo sapiens are a mosaic combination. Rather think of the human genome as a blueprint, think of it as a tapestry, combining fragments of DNA from our now-extinct hominin brethren. Yes, humans migrated out of Africa; but we also coexisted with ancient lineages of hominins.

Ancient DNA analysis is not just the basis for Jurassic Park out-of-control threats to human existence Hollywood scenarios. Long before ancient DNA became the basis of fictional blockbusters, biologist and anthropologist Svante Pääbo was developing the techniques of ancient DNA analysis which would open up the burgeoning field of paleogenetics.

Denisovans

Extracting, sequencing and cataloging ancient DNA would lead to the discovery that Homo sapiens interbred with Neanderthals. Not only that, but a completely new ancient hominin species was discovered, the Denisovans. Initially, the identification of Denisovans occurred based on the mitochondrial DNA extracted from a finger bone fossil, excavated from Denisova Cave, Siberia in 2010.

Since then, Pääbo and other researchers have done more work uncovering the mysterious Denisovans. Not only did they coexist with us, they also interbred with Neanderthals. The fossils of Denisovans are rare, and work on them has been painstaking. Nevertheless, scientists are starting to paint a fuller picture of the Denisovans, our evolutionary cousins.

Carl Zimmer, writing in the New York Times on the Denisovan origins, states that while fossils for the extinct lineage may be hard to come by, they make up for it with DNA. Indeed, Denisovan teeth and bones have been located in Laos and Tibet, indicating that they could survive in variegated climates and altitudes. It was not until 2019 that researchers found that Denisovans lived outside their ancestral home in Siberia.

In fact, Denisovan DNA fragments are extant in the genomes of indigenous people of Papua New Guinea. Researchers, in 2019, identified Denisovan DNA in modern day Papuan genomes, specifically how Denisovan contributions towards the immune system of Papuans. Not only did the Denisovans travel far and wide, they adapted to the various diseases they encountered along the way.

Darwin, fossils and the human genome project

It was the publication, in 1871, of Darwin’s book The Descent of Man, that really got tongues wagging about human evolution in the English-speaking world. Darwin barely mentioned human origins in his most famous work, On The Origin of Species. He covered all sorts of non-human species in his Origin book; barnacles, ants, aardvarks, lizards – you name it. He tiptoed around the topic of human origins, leaving that for a later date.

He tackled human evolution head on, in his Descent volume. The fossil record at the time was exceedingly thin, and he made a number of observations that have stood the test of time. Basing his case on comparative anatomy, embryology and behaviour, he hypothesised an African origin for Homo Sapiens.

So while he refrained from posing the definitive answer, he laid the foundations for others to follow. Darwin of course, never knew about DNA; that finding would not reveal itself until years into the future.

If there is one discovery that can truly be called epoch-making, it is the complete mapping of the human genome in 2001. While it is impossible to summarise the entirety of the genome project in one blog article, we can make a number of pertinent observations.

The unraveling the human genome was accomplished by much hyperbole about unmasking our true selves. The genome was compared to a blueprint, a CD-ROM of instructions if you will, and humans were supposed to be totally summarised by this finding.

Let’s not delude ourselves that we are reducible to genes. Language and culture, based on our labour power, is what makes us truly human. It is impossible to understand the emergence of humanity without understanding the decisive role of labour – bipedal locomotion freed up the hands from arboreal living.

To be sure, Neanderthals, Denisovans, even Homo Floresiensis – annoyingly nicknamed ‘hobbits’ because of their small stature – all demonstrated a level of toolmaking, symbolic production and the beginnings of stories and songs. As we uncover their genes, we need to make a careful analysis of their cultural environments, and the methods they used to shape it.