Pondering the big picture, what has changed in the last 100 years or so …

This article (republished from The Conversation under a Creative Commons license) is a useful recap of our understanding of human evolution, and an excellent visualization of that story, including salient talking points.

The millions-of-years history of our rise as a species is a fascinating story of patient pursuit of knowledge. A pursuit all too often underfunded and under-resourced, starting with singular archeological discoveries and growing into multidisciplinary collaboration. That joint research expanded the outlines of our story from bones & stones to geographic and climatic events, to genetic (DNA) arcs, and to social and cultural changes.

Much has been made of our species’ brain size. It’s interesting to see some myths dispelled on that score, as well as a summary of the tradeoffs of such development.

The timescale of this story is so beyond what we typically consider as history – removed so distantly from our livelihoods – that it’s more like mythology and cosmology. As this article notes, public interest is absent “except when an exciting find hits the headlines.”

This article contains visualizations: photos, charts, and videos.

• Wired > “The Whole Story of How Humans Evolved From Great Apes” by John Gowlett (Nov 28, 2024) – The picture of human evolution has changed repeatedly and dramatically over the past half century, shaped by waves of new fossil discovery, technology, and scientific techniques.

Outline

• Early Apes to “Hominization” (35 to 8 Million Years Ago)
• Earliest Hominins (7 to 4 Million Years Ago)
• Australopithecines (4.3 to 1.4 Million Years Ago)
• Beginnings of Homo (About 2.8 Million Years Ago)
• Talking Point: Who Made the First Tools?
• Homo Erectus (1.8 to 0.5 Million Years Ago)
• Talking Point: The Benefits of a Bigger Brain
• Modern Humans (300,000 Years Ago)
• The Great Breakout (100,000 Years Ago)
• Last of the Neanderthals (40,000 Years Ago)
• Talking Point: Art and Technology
• After the Ice (20,000 Years Ago)

Quotes

Yet, there is still some debate about whether the chimpanzee is our best model for the starting point: the “last common ancestor.” Better to call it the “best living model,” because the chimp has shown many adaptations of its own, especially in its limb proportions and locomotion, but also in its large shearing front teeth. But its social behavior, communication, and tool-making have all provided invaluable insights into the processes that we can call “hominization.”

In brain size, Homo erectus was certainly not static. Contrary to a general impression that most of the great brain enlargement in Homo is relatively recent, there was already some overlap with modern humans half a million years ago.

Although it is natural to think that to be clever is an end in itself, large brains like ours are costly enough to take 20 to 30 percent of our energy, and they have to pay their way. Most species succeed with far less than hominins, and to treble brain size in 2 million years is a remarkable phenomenon. Such an expansion was only possible through a high-quality diet and reduction in the size of other major organs.

As the large brain is energetically expensive, it must have had evolutionary drivers. One of the most appealing is the “social brain hypothesis“, whose core idea is that in some environments, ecological survival favoured larger groups. We know from regular stone tool transport distances of 5-10 km, and occasional ones of 20-30km, that hominins were ranging much further than apes even 2 million years ago. The social management of such groups is very demanding, and may have been a spur towards developing larger brains.

Until the 1980s, our species was thought to have first appeared around 40,000 years ago in a “human revolution” – an explosion of creativity marked by the flowering of cave art and sophisticated tools. However, many events in this analysis were incorrectly concertinaed together by a ceiling in radiocarbon dates, which the rapid decay rate of carbon-14 limited to a maximum age of about 40,000 years.

Since then, new dating techniques based on other radioisotopes and new finds have expanded the timescale for the existence of Homo sapiens by almost a factor of 10. In fact, the first early modern humans, closely resembling us, appeared about 300,000 years ago in northern and eastern Africa. This drastic change of timescale alters our perspective in ways that are still being explored.

Some of the clearest genetic signals come from parts of the genome that do not recombine each generation—that is, the Y-chromosome and mitochondrial DNA. These have allowed scientists to assemble “family trees” that show that all modern humans (Homo sapiens) are related within about 150,000 years.

In essence, this was a great population expansion rather than a migration. Populations remained in Africa and along the way, but this astonishing wave of advance headed east across Asia, then north into Europe, and ultimately to all parts of the world.

Historically, studies in human evolution greatly emphasized Europe. While the balance has rightly been redressed to a global perspective in the last 50 years,

The Neanderthals have an enduring fascination because they are so like us and yet so different. They were stocky and strong, and had a brain as large as ours. Their abilities have been debated for more than a century, but there is strong evidence that they are an alternative humanity rather than an inferior humanity. They had full control of fire, made bone tools, used pigments, and buried their dead.

From one of my poems (1998)

what is there to reply, to say?
pay the beast, we cannot stay.
we have left the trees, put up walls.
gone the warming fire-ring without,
the tribal whole within.
ascending lord of neoteny,
at home, we yet stand that grassy plain
and cut our path in moving on