Human evolution: A story still being written

This week’s episode of Big Biology features a re-release of our most popular episode: The Origin of Us: Human Evolution with Kate Wong. Wong is a Senior Editor at Scientific American where she has covered the field of biological anthropology for more than two decades. In the episode, Wong, Art, and Marty discuss the article she wrote to commemorate Scientific American’s 175th anniversary (which occurred back in 2020) entitled “How Scientists Discovered the Staggering Complexity of Human Evolution.” This week’s blog will provide a deeper dive into the various hypotheses of human evolution that they mention in the episode, as well as a look at the present-day relevance of human evolution research.

The Hypotheses

It wasn’t long after Darwin published his seminal book, On the Origin of Species , that biologists started debating the nature of human evolution. In her article, Wong mentions that Thomas Henry Huxley and Charles Lyell published the first books about human evolution in the 1860s, shortly before Darwin published Descent of Man in 1871. A lack of fossil evidence, however, and a general resistance to the idea that humans first evolved in Africa meant that early theories of human evolution were often influenced by racial biases, which slowed progress in understanding our species’ origins until new fossil discoveries in the 20th century began to clarify our evolutionary history.

In the mid-20th century, the Multiregional Evolution Hypothesis proposed that “Homo sapiens emerged from archaic populations that are found around throughout the Old World,” Wong explains. According to this view, gene flow between these populations prevented human ancestral species from diverging while allowing the different groups to maintain regional variation. The Multiregional model explained regional variation as the result of long-term local evolution, but it struggled to account for the growing fossil record. By the late 20th century, evidence (especially genetic data) was mounting that modern humans arose more recently in Africa, leading many scientists to favor a new hypothesis: Out of Africa.

In the 1980s, new fossil and genetic evidence started to shift the scientific consensus to the Out of Africa Hypothesis, which suggested that “modern Homo sapiens evolved in Africa, spread out across the world, and displaced all other hominids that were there.” The Out of Africa Hypothesis holds that modern Homo sapiens evolved in Africa between 200,000 and 300,000 years ago and migrated