Posted on 01/24/2006 3:43:03 AM PST by Pharmboy
AP - Mon Jan 23, 11:19 PM ET A research team led by Syracuse University biologist Scott Pitnick, pictured in Syracuse, N.Y., Monday, Jan. 9, 2006, found that in bat species where the females are promiscuous, the males boasting the largest testicles also had the smallest brains. Conversely, where the females were faithful, the males had smaller testes and larger brains. (AP Photo/Kevin Rivoli)
SYRACUSE, N.Y. - For some male bats, sexual prowess comes with a price — smaller brains. A research team led by Syracuse University biologist Scott Pitnick found that in bat species where the females are promiscuous, the males boasting the largest testicles also had the smallest brains. Conversely, where the females were faithful, the males had smaller testes and larger brains.
"It turns out size does matter," said Pitnick, whose findings were published in December in "Proceedings of the Royal Society: Biological Science," an online journal.
The study offers evidence that males — at least in some species — make an evolutionary trade-off between intelligence and sexual prowess, said David Hoskens, a biologist at the Centre for Ecology and Conservation at the University of Exeter in England and a leading authority on bats' mating behavior.
"Bats invest an enormous amount in testis, and the investment has to come from somewhere. There are no free lunches," said Hoskens, who did not participate in the study.
The relationship between the breeding system and relative brain size has received little investigation, said Pitnick, who teaches evolution and population biology and researches topics such as sexual selection and sexual conflict.
Bats are the second largest group of mammals (behind rodents) with about 1,000 known species. Because of their exceptional navigational and flying abilities, bats have been the subject of countless studies, providing Pitnick and his colleagues — Kate Jones of Columbia University and Gerald Wilkinson of the University of Maryland — with a bounty of data without having to slink off into caves.
Pitnick's team looked at 334 species of bats and found a convincing contrast in testes size. In species with monogamous females, males had testes starting at 0.11 percent of their body weight and ranging up to 1.4 percent. But in species where the females had a large number of mates, Pitnick found testes ranged from 0.6 percent to 8.5 percent of the males' mass (in the Rafinesque's big-eared bat).
"If female bats mate with more than one male, a sperm competition begins," Pitnick said. "The male who ejaculates the greatest number of sperm wins the game, and hence many bats have evolved outrageously big testes."
Promiscuity is known to make a difference in testicle size in some other mammals. For example, chimpanzees are promiscuous and have testicles that are many times larger than those of gorillas, in which a single dominant male has exclusive access to a harem of females.
Large brains, meanwhile, are metabolically costly to develop and maintain. Pitnick's research suggested that in those bat species with promiscuous females, the male's body used more of its energy to enhance the testes — giving it the greater adaptive advantage — and lacked the energy it needed to further develop the brain.
The study found that in more monogamous species, the average male brain size was about 2.6 percent of body weight, while in promiscuous species, the average size dipped to 1.9 percent.
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On the Net:
The Royal Society: http://www.pubs.royalsoc.ac.uk
Big family jewels, small brain ping list...
True enough...and it is also a bit misleading, since size usually refers to the penis rather than the testes.
"Quick...to the Batpole."
You did ... what!?! ... to bats?
What about the variations in weight among male bats? Wouldn't fat bats and or scrawny bats skew the sample?
See, God didn't need to use evolution, as Henry Ford did, because, unlike Henry, he could see the final product before he made the first one.
So - - - Bingo! He makes fish. Bingo! He makes horses. Bingo! He makes humans. Etc. Etc. Etc. All finished from the start.
Got it?
Promiscuous bats?
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I guess there is an intersection of the curves on the graph - a "sweet spot", if you will.
males had testes starting at 0.11 percent of their body weight and ranging up to 1.4 percent.s>>
1.4 percent of bodyweight! For a 170 lb male human that would be... hoo boy. Never mind.
LOL
Just hmmmmm, so is evolution all about sex or maybe sex is all about evolution?
I'm both stuned and beebed..over a dozen posts, and not one "big brain & little brain" comment..
Um.... I'm speechless.
That explains my Mensa membership.
Deja Vu all over again. This was posted two weeks ago.
I'm thinking someone mis-named this bat. It ain't just his ears that are big.
8.5% of their mass eh? In a 200 pound Human male, he'd have 17 pounds of uhm, er. I imagine it would chafe.
Get ready for the feminazis to jump on this . . .
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