Map Key
Homoheidelbergensis evolved into Denisovans and Neaderthals, later producing hominins in China
Modern humans emerged from Africa around 200,000 years ago, arriving in the Middle East between 120,000 to 80,000 years ago, and later spreading through Europe and Asia
Homoerectus descendants from the Middle East worked their way into Europe and Asia, giving rise to hominin populations and Homoheidelbergensis in Africa
Modern humans evolved in Africa from Homoheidelbergensis or a hominin from the Middle East, and moved into Eurasia over the course of several waves
Out on a limb
This is a story about our little branch on the tree of life. Let us journey out on a figurative limb, balancing our way along the branch we share with the primates, and then onto the smaller branch we call Homo. Thanks to advances in genetic technology, working in tandem with fragments of fossil evidence, we are starting to get a sense of where, geographically, this strand began.
The “tree of life” is a conceptual illustration of the interrelatedness of life, similar to the concept of the family tree, but grander in scale. This scientific endeavour is known as “taxonomy”, derived from two Greek words: taxis, which means order or arrangement, and nomos, which means law or science. Together, they form the branches of this elaborate tree structure.
Homo erectus 1.8million years ago ( YA)
The African Model The Asian Model neanderthals homo heidelbergensis
In taxonomy, every group has a sister group – its closest relative. You could think of the sister group as the neighbouring branch. The branching point is their last common ancestor. We share a relatively recent common ancestor with apes and monkeys, a less recent ancestor with all mammals, and a distant ancestor with all other animals. If you journey into the past, you will find that all living organisms share a common ancestor.
Let’s see where humans are situated on this tree, and examine the research that seeks to determine when, and from where, these branches evolved. Where on Earth did modern humans evolve? Where did apes come into being? Who is our closest relative? To place any organism on the tree of life, there are three main lines of scientific inquiry: living anatomy, fossil anatomy, and genetic research.
Comparative Anatomy
The earliest efforts to place humanity on the tree of life followed the most obvious point of investigation: The shared anatomy of living organisms. It’s apparent that two different species of pine tree belong in the same category, and it’s clear that the squirrels of the world are related to one another. While there are some organisms that – superficially – resemble one aother (koalas and pandas, sharks and dolphins), careful study of specific anatomical features can help reveal the true relationship between species.
It’s become clear that we are most closely related to the great apes: the chimpanzee, gorilla, and orangutan. Anatomically, the differences are minor; we have almost exactly the same internal organs and remarkably similar skeletons. Tellingly, at various points, our vocabulary has
About 200,000 years ago, our own recognisable lineage, Homo sapiens, appears in the African fossil record, and 100,000 years ago, groups began migrating outwards into Eurasia, possibly in several waves.
Dr Rainer Grün, Director and Inaugural Professor of Archaeogeochemistry at the Australian Research Centre of Human Evolution at Griffith University, contextualises the progress in the study of human evolution: “When I started my career, modern humans evolved in Africa around 50,000 years ago and migrated straight to Europe,” he says. However, it now seems that rather than occupying Ice Age Europe, modern humans turned east to migrate to China, Southeast Asia and down to Papua New Guinea and Australia, he explains.
Dr Grün adds that these early migrants encountered Homo erectus, as well as other human species, such as Homo floresiensis – and possibly some species that we have not even discovered yet. He expects that new fossil finds from Southeast Asia will make significant contributions to our understanding of human evolution.
Asian Primate Fossil Discoveries
In research circles, there has been a refinement of models of human evolution, including in Asia. Dr Colin Groves, Emeritus Professor in the School of Archaeology and Anthropology at Australian National University, explains: “There used to be a vague feeling that the human lineage arose in Africa. Then there was Homo erectus, known from just two sites or groups of sites in Asia [Zhoukoudian near Beijing, and Trinil, Sangiran and Ngandong in Central Java]. For all we knew, the locus of human evolution might have simply moved to eastern Asia, and then moved back again.”
Back then, the relationship of Asian Homo erectus to modern peoples in Asia and Australasia was not known, but now, the picture is much clearer. “The Chinese and Javanese fossils are different from each other and from their contemporaries in Africa, and were essentially sidelines as far as human evolution is concerned, although they show our ancestors dispersing far from Africa and occupying unfamiliar environments,” Dr Groves explains.
Like Us
Overlapping with our modern human time frame are other lineages of Homo that had left Africa, including the Neanderthals (known from across Eurasia), Flores Man, or “hobbits” (known from skeletons found in Indonesia), the Denisovans (known from DNA evidence from teeth and a finger-bone from a single cave in Siberia), and the Red Deer Cave People (known from bones in caves from Central China).
Modern humans mingled with Denisovans and Neanderthals, and with new genetic tools, we have been able to identify portions of the modern genome that come from these distinct groups. Recent research indicates a previously unknown population of early humans in Southeast Asia that connected with the first of modern humans to travel through Asia and on to Australia and New Guinea.
For Dr Michael Westaway, Head of Palaeoanthropology Research at the Australian Research Centre of Human Evolution at Griffith University, the discovery of