Humans evolved a robust inflammatory response to fight constant threats like infections. In today's relatively sterile world, this powerful system lacks its historical targets and can overreact to modern triggers, leading to the chronic low-level inflammation that is at the heart of many modern diseases.

Early hominins were heavily exposed to lead in cave water. New research suggests a genetic mutation unique to modern humans protected the brain's language centers from lead-induced damage. This neurological resilience could have provided a critical evolutionary advantage over species like Neanderthals, preserving vital communication skills.

Contrary to expectations of increasing societal complexity, the strongest selection for genetic variants predicting modern IQ test scores and educational attainment occurred between 4,000 and 2,000 years ago. In the last 2,000 years, including the industrial revolution, there has been no detectable selection on these traits.

While hunter-gatherer life seems cognitively demanding, their genetic profile predicts dramatically lower scores on modern intelligence tests. The subsequent rise in Europe's average score was driven primarily by the migration of farming populations with a different genetic setpoint, not gradual evolution within the hunter-gatherer lineage.

Once a population reaches millions, every possible mutation occurs regularly. Therefore, the rapid selection seen in the Bronze Age wasn't enabled by larger populations creating more variants. Rather, it reflects sufficient time (thousands of years) for strong selective pressures to act on existing genetic variation.

Contrary to popular belief, cereal farming was less efficient for feeding people than horticulture. Its dominance stems from the necessity to develop complex tools, materials, and machinery (plows, kilns, irrigation) to survive in drier climates, which inadvertently drove technological advancement and empire-building.

All populations that developed agriculture descend from ancestors who lived long before its invention, implying the necessary cognitive abilities were in place. The simultaneous, independent emergence of farming worldwide points to a global environmental trigger: the unprecedented climate stability of the last 12,000 years (the Holocene).

Primatologist Richard Rangham's theory posits that early hominins used fire for cooking. This made food more energy-efficient to digest, freeing up metabolic resources that enabled the evolution of our larger brains. We didn't just get smart and then cook; we cooked, and that's how we got smart.

The TYK2 gene variant, a risk factor for tuberculosis, increased in frequency for thousands of years before plummeting in the last 3,000. This suggests it protected against an earlier threat but became a liability with the rise of endemic tuberculosis in denser populations, showing how selection can reverse direction.