Friday, December 14, 2012

When being short is adaptive

As a tall person, I've always been told that I had an advantage in life - indeed, height correlates with some metrics of success.  However, researchers at the University College London that there are actually cases where it is evolutionarily advantageous for individuals to be shorter.

The researchers examined 89 small populations from various environments across the world who employed various subsistence strategies, then performed statistical analyses to determine what factors proved predictive of height.  While there was some effect of environment and a very minor role of diet, the strongest correlates were measures of life expectancy.  The shorter the projected lifespan of a population, the shorter the people would physically be.  This makes intuitive evolutionary sense -- if you're likely to die young, you should stop devoting energy to development earlier on in life so that you can start devoting energy to producing offspring.  This shorter development window (which also correlates with earlier onset of menstruation) means that individuals have less  time to grow.   On the other hand, if you're going to live longer, the increased energy associated with being larger would ultimately permit you to later devote more energy to reproduction.

While these findings were for modern human populations, they actually are informative for further back in our evolutionary history; as we evolved from australopthecus ancestors into the homo genus, increased intelligence might have brought about increased lifespan, allowing the more recent ancestors of humans to grow taller than their more apelike ancestors.

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