Spicy Ideas From Evolutionary Biology - Dr Jerry Coyne

The Central Thread: Speciation and the Origin of Species

Dr. Coyne begins by reflecting on his scientific journey, which was largely devoted to the problem of speciation—the origin of species—a question that Charles Darwin famously posed but never fully solved. While Darwin’s 1859 book, On the Origin of Species, laid the foundation for evolutionary biology, Coyne points out that Darwin knew very little about how species arise as discrete, “lumpy” entities rather than as a continuous spectrum. This “lumpiness” of nature, where organisms fall into distinct species rather than blending gradually, remains a fundamental puzzle.

Coyne explains that the key to understanding speciation lies in reproductive isolating barriers—mechanisms that prevent gene flow between species. These barriers can be biological, such as hybrid sterility or inviability, or behavioral, like differences in mating preferences or timing. For example, lions and tigers can produce hybrids in captivity but do not interbreed in the wild due to behavioral and ecological barriers. The challenge, Coyne notes, is to explain how these barriers evolve in a continuous evolutionary process, a question that drove much of his research.

Advocating for Evolution Amidst Ideological Opposition

Coyne’s career has also been marked by his efforts to defend evolutionary theory against creationist and anti-evolutionary attacks. He recounts how early evolution textbooks often assumed evolution as a given, neglecting to present the overwhelming evidence supporting it. This gap motivated him to write Why Evolution is True, a book aimed at making the scientific case for evolution accessible and clear.

The conversation highlights the ironic political dynamics surrounding evolution. Historically, left-wing groups used evolution as a weapon against right-wing religious beliefs, but now, Coyne observes, the right often uses evolutionary arguments—particularly evolutionary psychology—to challenge left-wing ideologies. This tug-of-war reflects how evolution has become a cultural battleground, with both sides selectively embracing or rejecting aspects of evolutionary science to support their political narratives.

Coyne emphasizes that acceptance of evolution is generally higher on the political left, but even so, a significant portion of the American public rejects naturalistic evolution. Polls show that only about 23% of Americans accept a fully naturalistic, unguided evolutionary process, while the majority either believe in creationist views or a hybrid “theistic evolution.” This widespread skepticism poses ongoing challenges for science education and communication.

Evolutionary Psychology: From “Just-So Stories” to Scientific Maturity

The discussion turns to evolutionary psychology (EP), a field that Coyne initially viewed skeptically due to its early reliance on speculative “just-so stories” to explain human behavior. However, he acknowledges that EP has matured, with researchers increasingly formulating testable and falsifiable hypotheses. Coyne cites recent work demonstrating that evolutionary psychology can make predictions subject to empirical scrutiny, moving it closer to the rigor of other evolutionary disciplines like molecular genetics.

Despite this progress, EP remains controversial, especially because it challenges deeply held ideological beliefs about human nature and behavior. Coyne notes that evolutionary psychology is often unpopular on the political left because it implies biological constraints on human behavior, which conflicts with ideals of social malleability and equality. This ideological resistance parallels similar pushback against behavioral genetics, which also reveals genetic influences on traits and behaviors.

Coyne and his colleagues have documented how ideology distorts biology, identifying six key areas where scientific facts are misrepresented or suppressed. These include denial of biological sex differences, rejection of race as a biological concept, and the elevation of indigenous knowledge systems as equivalent to modern science. Coyne laments how ideology has begun to erode scientific integrity, not only in biology but also in fields like physics and mathematics.

The Biological Reality of Sex and Race

Coyne is particularly outspoken about the biological basis of sex, asserting that there are only two sexes—male and female—defined by reproductive roles and anatomy. He argues that this binary is universal across animals and plants and is fundamental to understanding sexual selection and behavioral differences between males and females. Coyne criticizes the growing cultural trend to deny or blur this binary, which he sees as ideologically motivated rather than scientifically grounded.

Similarly, Coyne addresses the contentious issue of race, acknowledging that while the concept of race is socially fraught and poorly defined, there are clear genetic differences among human populations. He explains that genetic clustering corresponds closely with self-identified race or ethnicity, reflecting historical patterns of geographic isolation and gene flow. Coyne stresses that denying these biological realities does not serve science or society.

Speciation Timelines and Human Evolutionary History

The conversation explores how long it takes for species to form, with fruit fly studies suggesting that reproductive isolation can develop over one to two million years of geographic separation. In primates, humans and chimpanzees diverged around seven to eight million years ago, clearly distinct species. By contrast, modern human populations have only been separated for tens of thousands of years, insufficient time for speciation.

Coyne discusses the interbreeding between Homo sapiens and Neanderthals, noting that their offspring were viable and fertile, as evidenced by the presence of Neanderthal genes in modern human genomes. He also touches on the enigmatic “hobbit” species, Homo floresiensis, which was remarkably small and lived as recently as 12,000 years ago. Coyne speculates that island dwarfism, driven by limited resources, likely explains their small stature, a phenomenon observed in other animals as well.

Adaptations and Human Diversity

Coyne explains some adaptive reasons behind human physical diversity, such as skin pigmentation correlating with ultraviolet radiation levels. Darker skin protects against sun damage in equatorial regions, while lighter skin facilitates vitamin D synthesis in areas with less sunlight. He also mentions body shape adaptations to climate, like the stocky build of Arctic populations to conserve heat, consistent with Allen’s rule observed in other animals.

However, Coyne admits that many traits, such as hair and eye color, remain poorly understood in terms of adaptive significance. He stresses the importance of scientific humility and acknowledges the limits of current knowledge.

The Ideological Erosion of Science and Challenges in Communication

Coyne expresses concern about the increasing self-censorship and ideological pressures within academia and media. He cites examples such as the reluctance to report ethnicity in crime stories and inconsistent editorial practices that valorize minority groups symbolically. He introduces the concept of “gamma bias,” where gender issues are amplified or minimized depending on the victim’s or perpetrator’s sex, reflecting societal double standards.

Coyne recounts his own experiences confronting controversial topics like sex and gender, including his rebuttal to a transgender-affirming article that was quickly removed by the organization that published it. He advocates for civil, honest discourse grounded in biological facts, rejecting the need for excessive disclaimers or ideological concessions. Coyne warns against the “reverse naturalistic fallacy,” where people expect nature to conform to their political or personal beliefs rather than accepting empirical reality.

He also reflects on the broader cultural dynamics, noting how guilt over historical injustices has fueled overcorrections and ideological overreach, which may ultimately undermine social cohesion and scientific progress. Coyne remains uncertain about the future trajectory of these cultural battles but emphasizes the enduring importance of truth and evidence.

The Disgenic Theory and Genetic Load

Toward the end, Coyne discusses a provocative and somewhat controversial idea related to the accumulation of genetic mutations in humans due to relaxed natural selection. With modern medicine and technology mitigating many selective pressures, deleterious mutations may accumulate over generations, potentially leading to a “crumbling genome.” He compares this to selective breeding in dogs, where artificial selection has produced health problems.

Coyne acknowledges the complexity of this issue, including the challenges of genetic engineering and the ethical minefield surrounding eugenics. He stresses that while medical advances have extended human lifespan and quality of life, they may also allow the persistence of mutations that would have been eliminated ancestrally.