Aspire to be both strong and fast? Turns out you probably can't be both.
A recent study published in the journal Behavioural Processes found that the size and width of a dog's head can predict his strength and speed. Not only does this finding apply to dogs, but it may relate to other animals, including humans, as well.
William Helton, with the University of Canterbury's Department of Psychology, studied over 200 dogs at the International Weight Pulling Association events, reports Discovery News. The broad-headed (Brachycephalic) dogs, including American Pit-Bull Terriers, American Bulldogs and Bernese Mountain Dogs, were able to pull noticeably more weight than the narrow-headed (Dolichocephalic) dogs, including Samoyeds, Siberian Huskies and Alaskan Malamutes. But on the flip side, past studies have shown that narrow-headed dogs are faster and more efficient at running than broad-headed dogs.
Another study claims that humans can rather accurately predict a man's strength just by looking at a picture of his face. Don't judge a book by its cover, but perhaps it is appropriate to judge a man's strength by his face...
The human head is narrower than other great apes, and Helton suggests that humans have adapted to run for long durations at the expense of strength. Endurance appears to have been important to our ancient hominid ancestors, who probably chased their prey to death.
Certainly head size isn't the only factor in determining the speed and strength of an animal. Nutrition and conditioning play a key role. But the study does demonstrate that we often can't have it all. As Helton explains, "Nature does not allow unlimited budgets and the trade-offs are often physical constraints."