Human evolution

When did modern Homo sapiens evolve, and what was early human life like?

Modern Homo sapiens evolved approximately 300,000 years ago. Until around 10,000 years ago, all humans were hunter-gatherers living in nomadic groups with temporary camps and a total global population of only hundreds of thousands to a few million individuals.

What does evidence from modern hunter-gatherers suggest about early human diets?

Modern hunter-gatherer groups show varied diets with latitudinal differences. Importantly, the common view that males only hunted and females only gathered is false — both sexes participated in both activities.

What is the Out of Africa theory and what are the key migration timelines?

Modern humans originated in Africa and expanded outward. Ancestors of Australian Aborigines took a coastal route through India and SE Asia to Australia ~80,000 years ago. Eurasians moved into the Middle East, Europe, and Asia ~50,000 years ago. Amerindians moved into the Americas ~35,000 years ago, followed by island colonisations.

What happened to large mega-fauna as humans spread?

Large mega-fauna declined over time — there was an increase in extinctions and a decrease in large carnivore and mega-herbivore species (size 3 and 4 carnivores) as human populations expanded (Faith et al. 2020).

What does the evidence say about whether early humans caused mega-fauna extinctions?

The evidence is disputed. Lemoine et al. (2023) found models including human factors outperformed purely climatic models, suggesting human-driven environmental transformation played a role. However, Faith et al. (2020) found no compelling evidence for deep hominin impacts in Africa, attributing the loss of only three taxa to Homo species over at least a million years — insufficient to warrant a unique anthropogenic extinction mechanism.

How many Homo species are known to have existed, and which survive today?

At least nine Homo species existed: H. sapiens, H. neanderthalensis, H. denisova, H. erectus, H. luzonensis, H. naledi, H. floresiensis, the Red Deer Cave People, and H. sapiens. Today only H. sapiens survives.

What are the leading explanations for the extinction of other Homo species?

The causes are disputed and no single explanation is agreed upon. Evidence points to rapid climate change reducing climatic niche space just before extinction (Raia et al. 2020), particularly for H. erectus, H. heidelbergensis, and H. neanderthalensis. Competition with H. sapiens likely exacerbated the decline of H. neanderthalensis.

What is the evidence for interbreeding between H. sapiens and H. neanderthalensis?

Interbreeding and hybridisation is traced back to at least 47,000–65,000 years ago. Neanderthal DNA in modern humans may be less than 2%. A Neanderthal-Denisovan F1 hybrid was discovered (Slon et al. 2018). Models suggest interbreeding played a bigger role under low resource competition (Timmermann 2020).

What were the mutual benefits that likely drove wolf domestication?

Wolves benefited from scavenging near humans, receiving food scraps, shelter, and protection from other predators. Humans benefited from assistance with hunts, warning signals about threats, companionship, and the psychological deterrent effect of a fierce animal.

What did genetic evidence reveal about dog domestication?

Dogs likely arose once from a now-extinct wolf population. By 11,000 years ago, at least five major ancestry lineages had diversified. Dog population history mirrors human history in several ways, including a near-complete turnover of Neolithic European dog ancestry.

When and why did agriculture develop?

Rapid, large-scale domestication of plants and animals occurred approximately 10,000–7,000 years ago. This shift is linked to a climate improvement in the early Holocene (Gupta 2004). Agriculture made possible the complex, large, technologically innovative human societies that exist today.

What was the bridge between nomadism and settlement?

Herding

What were the first plant species to be domesticated and where?

Wheat was domesticated ~9,000 BC in the Middle East; rice ~6,000–11,000 BC in China; and maize ~5,500–10,000 BC in Mexico. These were derived from wild ancestors

How has melanin evolved in human populations and why?

There is high variation in melanin across human populations, correlating with latitude — lighter skin at higher latitudes. This reflects selection linked to UV radiation and the need for vitamin D3 synthesis: darker skin protects against UV damage in high-sunlight regions; lighter skin maximises vitamin D production at low UV latitudes (Parra 2007).

How have Sherpas adapted to high-altitude living?

Sherpas have retained endothelial function above 4,000m elevation compared to lowlanders, demonstrating genetic adaptation to oxygen-scarce high-altitude environments (Tymko et al. 2019).

How does the sickle-cell gene illustrate recent human evolution?

In areas of heavy malaria (particularly the tropics), the sickle-cell gene causes malaria-infected blood cells to self-destruct, reducing malaria density in carriers. Children with the gene have improved malaria resistance, so the gene is maintained by natural selection in these regions despite causing sickle-cell disease in homozygotes (Luzzatto 2012).

How did cranial capacity change across Homo species?

Cranial capacity evolved rapidly over approximately 3 million years, increasing progressively across Homo species. Cranial capacity is used as a proxy for increased intelligence — larger skulls indicate larger brains.

What role did economics play in the extinction of H. neanderthalensis?

Division of labour and trade among early modern humans may have allowed H. sapiens to overcome biological deficiencies. Trade could have partially offset natural selection, enabling H. sapiens to thrive while outcompeting and driving H. neanderthalensis to extinction.

What is cultural evolution and does it qualify as evolution in the Darwinian sense?

Cultural evolution is the evolution of technology, ideas, and language rather than DNA. Darwin's mechanism only requires that variation be heritable — not that DNA is the basis of heritability. Since cultural traits vary, are heritable (transmitted between generations), and some survive better than others, cultural evolution qualifies as a Darwinian evolutionary process.

Does inheritance require DNA?

No. Darwin's evolutionary mechanism requires only that variation is heritable. RNA viruses (e.g. flu, HIV, Ebola) encode heritable variation without DNA. Any molecule or system that can encode and transmit information could in principle support evolution.

How does cultural evolution give humans an ecological advantage?

Rather than needing genetic adaptation for each new resource or environment, humans can simply acquire new behaviours (making spears, fishhooks, sickles) to exploit that resource. This allows exploitation of an extraordinary range of ecological niches far faster than genetic evolution would permit.

How did the pace of cultural evolution change in H. sapiens?

Cultural evolution in H. sapiens accelerated exponentially compared to earlier Homo species — rapidly advancing in technology, medicine, and language over just the last few hundred thousand years, in contrast to the static Acheulean culture lasting over a million years.

How can cultural evolution drive genetic evolution?

Cultural evolution can rapidly shift a population into a new ecological niche (e.g. learning to fish). If a behaviour is passed to offspring, more individuals exploit the new resource, creating selection pressure for genetic adaptations to that niche (e.g. larger cranial capacity for more complex tool use). Culture and DNA evolution can therefore interact and accelerate each other.