I recently got a Lyft ride from a man who majored in biology as an undergraduate years ago. He had always suspected that Neanderthals and modern humans interbred. Illustrating his point with the example of incredibly tall white basketball players with massive brow ridges, he mentioned that there are many people around today with traits commonly associated with a Neanderthal phenotype.
I acknowledged that some Neanderthal-introgressed genes do appear to have phenotypic consequences in modern humans, though his particular example struck me as unreasonable. The average Neanderthal male, at around 5’4″, was actually a bit shorter than contemporary white guys tend to be. How could Neanderthal ancestry contribute to the towering frame of, say, 7’7″ Gheorghe Mureșan?
Well, it turns out that Neanderthals were probably at least as tall, if not taller than early Europeans. What’s more, researchers have found that some people of European ancestry have a Neanderthal variant of ADAMTSL3, a gene associated with height. This still doesn’t mean that Neanderthal ancestry is responsible for tall white guys.
First of all, it’s unclear exactly how the Neanderthal variant affects height relative to the modern human one. From what I can tell, all we can say is that the Neanderthal variant has reduced expression in the people who have it. The genetics of height are also incredibly complicated. There may be at least 700 genes that contribute to height in modern humans.
Genetics isn’t everything, either. Environment plays a large role in how tall a child can grow. 20 – 40% of the variation in height between people is not genetic at all, but is due to the conditions in which they were raised. Mr. Mureșan may have reached a height close to the maximum allowed by his particular genetic profile. If he’d have gotten less to eat as a child, he may have been a bit closer to normal-sized.
As for the massive brow ridges, many athletes may have this trait simply due to high testosterone levels.