Personal experience suggests that if you put human males beside a body of water with a supply of stones to hand, they will soon start throwing them into the water. What drives them to do this, and is the same true of females? Is this unique to humans, or has it been observed in other primates? What purpose can it possibly serve?
鈥� I have just listened to a radio programme by David Attenborough about the aquatic ape theory, and it strikes me that this question fits well with this hypothesis.
Thinking of our environment, we struggle to picture the land or sea in pre-industrial times when both were teeming with animals. Our distant shore-living ancestors would have been constantly scanning the water for fish or other marine food animals, and lobbing stones would surely have been a simple way of killing a few.
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Maybe the skill was translated to throwing slings, boomerangs, spears and so on when humans later made hunting excursions further inland.
Since young men would naturally compete against one another with their hunting skills, males skimming stones seems another argument for the aquatic ape theory.
Stella Perrett, Bristol, UK
鈥� Many primates throw rocks, faeces and sticks, and some chimps have been known to throw rocks at zoo visitors. Some bonobos throw rocks at their preferred male to indicate they鈥檙e ready to mate.
However, heaving stones into water with no obvious hunting intent seems to be the preserve of Homo sapiens. Some theorise that this is a fish-hunting activity but, if so, the results are abysmal.
Given some rocks, water and nothing else to do, humans quickly become competitive, battling to see who can make the largest splash, skip a flat rock the furthest or hit a floating target. This clearly provides hunting practice, but is also classic play behaviour, think cats and their prey.
鈥淢any primates throw rocks, faeces and sticks and some chimps throw them at visitors to zoos鈥�
The 鈥渘othing else to do鈥� factor is important, and also suggests play behaviour.
Ron Dippold, San Diego, California, US
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This article appeared in print under the headline 鈥淣o stone unthrown鈥�