Human Evolution and Diversity

In Through the Lens of Anthropology we read the second of three parts of chapter 4, “Human Biological Evolution” and then discussed Human Evolution and Diversity:

These materials were for Intro to Anthro 2022. This class concentrated on the genus Homo. The previous class speculated on walking and bipedalism and at the end we set up the next class on how Race is not a valid biological concept.

Human Evolution and Diversity: From Bipedalism to Homo sapiens

The emergence of bipedalism marks a crucial turning point in human evolution and diversity. By approximately 3-3.7 million years ago, we have definitive evidence of habitual bipedalism among the Australopithecines in Africa. This mobility became fundamental to human evolution, setting the stage for the emergence of the genus Homo.

Homo erectus, appearing around 1.9 million years ago, represents a significant advancement in human evolution and diversity. These hominins exhibited increased cranial capacity and height, with some specimens reaching over six feet tall. They developed more sophisticated tool-making traditions, including the famous hand axes, and likely used fire. Importantly, Homo erectus was the first hominin to expand beyond Africa, spreading into Eurasia and Southeast Asia between 1.8 and 1.3 million years ago.

Confessions of an Extreme Lumper

I’ll admit it: I’m an extreme lumper when it comes to human evolution and diversity. While some researchers get excited about every new jawbone, proclaiming new species left and right, I tend to see more continuity. This isn’t just personal preference–though I do think we’re in an age where too many people are trying to divide us and tell us how different we are. The science of the past 20 years has shown that many of these supposedly distinct species were actually very much involved in the genetic mixture that makes up contemporary human diversity.

For example, I’m not big on Homo heidelbergensis. It’s an over-representation of European content, and there’s too much confusion about what exactly it represents. For me, it’s all in the range of Homo erectus. I’m not going to take off points if you’re a splitter, but for the purposes of your exam, you should be happy I’m a lumper. Less to memorize!

Neandertals & Endurance Running in Human Evolution

Neandertals, emerging around 400,000 years ago and coexisting with Homo sapiens until about 40,000 years ago, represent a well-documented hominin species in the story of human evolution and diversity. They were generally more robust than Homo sapiens and had a larger average cranial capacity, though there was significant overlap. It’s important to note that brain size doesn’t necessarily correlate directly with cognitive abilities. Evidence suggests Neandertals engaged in complex behaviors such as burial practices, tool use, and caring for sick or elderly members of their groups.

There’s been a lot of excitement about endurance running in human evolution. The idea is that our bipedalism, combined with our ability to sweat and control body temperature, allowed early humans to run down prey over long distances. When I grew up in Montana, I knew someone who could actually run down deer once the snow fell–you’d get on the deer tracks and just keep going. It’s pretty impressive, but we shouldn’t get too carried away. There’s contradictory evidence, and other forms of hunting were likely important too. The endurance running hypothesis remains a topic of debate among researchers studying human evolution and diversity.

The Emergence of Homo sapiens & Competing Models

Homo sapiens first appeared in Africa approximately 300,000 years ago, with the oldest fossils recently discovered in Morocco. Our species eventually spread across the globe, becoming the first and only hominin to reach Australia and the Americas, contributing to the diversity of human populations we see today.

Two main models have been proposed to explain the emergence and spread of Homo sapiens in human evolution and diversity:

  1. The Multi-regional Evolution or Regional Continuity Model, proposed by Franz Weidenreich in 1946, posits continuous gene flow across geographical ranges, evolving as a single interbreeding species.
  2. The Replacement Model, also known as “Out of Africa II” or “Mitochondrial Eve,” suggested that modern humans replaced other hominin populations without significant interbreeding.

The Admixture Surprise & Implications for Human Diversity

I still remember when my dad showed me the copy of Newsweek with the stylized “Adam and Eve” on the cover, promoting the Replacement Model. For a while, it seemed like this model had won the day. But then came what I call the “admixture surprise.”

Recent genetic evidence has revealed a more complex picture of human evolution and diversity. Studies from 2010 onward have shown evidence of interbreeding between Homo sapiens and other hominin groups, including Neandertals and Denisovans. As John Relethford of SUNY-Oneonta proposed, a “mostly out of Africa” model seems to best fit the current evidence of human evolution and diversity. This model acknowledges that while most human evolution occurred within Africa, there were multiple migrations and genetic exchanges with other hominin populations.

Recent Discoveries & the Second Cranial Revolution

Recent findings, such as Homo floresiensis and Homo naledi, have challenged our understanding of human evolution and diversity. These species demonstrate that complex behaviors and tool use were possible without significant increases in brain size, leading to what some call the “second cranial revolution” in our understanding of human evolution. However, it’s important to note that the exact place of these species in human evolution is still debated among researchers.

The Homo floresiensis, or “Hobbit,” finds are particularly intriguing. When I Googled them, the top questions were about how tall they were (short!), whether they’re still alive (sadly, no), and if they’re really hobbits (well, sort of?).

Key Points in Human Evolution and Diversity

  • Diversity and variation are essential to evolutionary processes.
  • Fitness is relative to ever-changing environments, involving trade-offs rather than simple “survival of the fittest.”
  • Organisms actively influence their environments, participating in niche construction.
  • Random events play a significant role in evolutionary outcomes.
  • Until relatively recently (~40,000 years ago), our ancestors regularly interacted with diverse bipedal species.
  • Humans emerged as a single interbreeding species across the world, representing a subset of earlier variation. While we’re often described as a “relict species”–the only surviving hominin–it’s important to note that we’ve undergone significant evolution and diversification ourselves.
  • We should be cautious about attempts to categorize or hierarchize human populations based on biological traits.

In conclusion, the story of human evolution and diversity is one of continuous movement, adaptation, and genetic exchange. It cautions us against simplistic categorizations of human populations and reminds us of the fundamental unity of our species despite our superficial differences. And remember, if you had to choose between being a Neandertal or a puny Homo sapiens 40,000 years ago, you might have put your money on the wrong horse!

Recap: Human Evolution and Diversity

In Through the Lens of Anthropology we read the second of three parts of chapter 4, “Human Biological Evolution” and then discussed Human Evolution and Diversity:

These materials were for Intro to Anthro 2022. This class concentrated on the genus Homo. The previous class speculated on walking and bipedalism and at the end we set up the next class on how Race is not a valid biological concept.

Related

One of the goals of this website was to encourage more accurate understanding of the “admixture surprise” of 2010. Related material on this website includes:


Living Anthropologically means documenting history, interconnection, and power during a time of global transformation. We need to care for others as we attempt to build a world together. This blog is a personal project of Jason Antrosio, author of Fast, Easy, and In Cash: Artisan Hardship and Hope in the Global Economy. For updates, subscribe to the YouTube channel or follow on Twitter.

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