Yao Ming, erstwhile NBA superstar and current wildlife campaigner stands 7 feet 6 inches (2.29 meters) tall. The average young man in China, by contrast, is 5 feet 9 inches tall (1.75 meters). This is far taller than a generation ago thanks to China’s vastly improved economic conditions, as lavish animal-protein hot pots have progressively replaced austere rice bowls. But the gap between the former professional basketball player and his fellow citizens spotlights the reality that height is one of the most salient of our variable human traits (Yao Ming’s parents both played basketball and their union was facilitated by the PRC’s army). Common sense tells us that Yao Ming is much taller than average not due to chance or exceptional nutrition; he was simply born to very tall parents and so was likely to be tall himself.
Not only does height vary greatly within populations, it also varies significantly between them. Men of the Dinka tribe of southern Sudan stand 6 feet (1.83 meters) tall on average. A few hundred miles to the south, men of the Efe tribe of the Democratic Republic of Congo average 4 feet 8 inches (1.42 meters) in height. The Efe are one of the “Pygmy” peoples of Central Africa, who are defined by their small stature. Both populations descend from common ancestors within the last 100,000 years, but evolution has produced very different average heights between the two groups.
From the perspective of a geneticist, human height has long been known to be one of the most heritable of characteristics. There is clearly variation between families and populations, and being tall or short runs in particular lineages. Today we are finally arriving at a good accounting for height’s biological underpinnings and can pinpoint the genomic differences which account for this variation. As a trait that is subject to natural selection (albeit weak and variable), the average height of human populations has shifted upward and downward several times over the course of our species’ evolutionary history. There’s also a reason that men exaggerate their heights on dating profiles. Being tall isn’t just useful when it comes to playing basketball or spotting predators on a savanna, its fortunes have long been driven by sexual selection, at least in males (the majority of male American CEOs are over 6 feet tall, even though only 15% of the male general population is).