Bettmann/Getty Images
Why do we scream in fear? It doesn’t help and makes us more vulnerable to predators (continued)
Ron Dippold
San Diego, California, US
There actually is some small benefit for the screamer. I have been hiking with someone who encountered a brown bear. She screamed. The bear was (apparently) freaked out by the scream and ran away at high speed. I have run into a couple of bears myself without conflict, and you should realise that most predators are not bloodthirsty maneaters. They have far more to fear from humans than vice versa.
“ The genes for screaming preserve themselves in our relatives (though sadly, often not in the screamer) “
But assume you are a neolithic human around the campfire and a bloodthirsty leopard who only wants to feast on human flesh wanders near your camp and runs into you on the periphery. You scream. This has two minor advantages for you: first, it lets your comrades know where to find your body – maybe you won’t be quite dead and can be dragged back, or at least they know where your corpse is. But more importantly, you have let your tribe members know there is danger and where it is. Your scream is mostly not for yourself – it’s so your relatives can survive.
James V. Stone
Buxton, Derbyshire, UK
When we scream in fear, it does indeed make us more vulnerable to predators. But it makes those around us less vulnerable to them, and if those around us are related to us, then they share some of our genes. Consequently, the genes for screaming preserve themselves in our relatives (though sadly, often not in the screamer).
Thus, our screaming is more likely to benefit the genes for screaming if those around us also possess these genes, and this is more likely if those around us are our close relatives.
The logical endpoint of this kin selection hypothesis is known as Hamilton’s rule (1964). This states that altruistic behaviour – in this case, screaming – persists if the fitness cost, C, to the altruistic individual is less than the overall fitness benefit, B, to the recipient, multiplied by the closeness, r, of their relation. Or, C < Br.
For example, Belding’s ground squirrels make alarm calls most frequently when their close kin are within earshot. So, screaming makes us more vulnerable to predators, but it also helps the genes for screaming in our relatives to survive into the next generation.
To answer this question – or ask a new one – email lastword@newscientist.com.
Questions should be scientific enquiries about everyday phenomena, and both questions and answers should be concise. We reserve the right to edit items for clarity and style. Please include a postal address, daytime telephone number and email address.
Â鶹´«Ã½ retains total editorial control over the published content and reserves all rights to reuse question and answer material that has been submitted by readers in any medium or in any format.
