With Big Brains Comes Fewer Offspring

Ben Parker once said to his nephew Peter, "With great power comes great responsibility".

Scientists recently discovered that there is a trade-off in intelligence as well--with great intelligence comes fewer offspring. At least in the case of guppies. 

Image: aqua-fish.net

In fact, the 2006 movie "Idiocracy", starring Luke Wilson and Maya Rudolph, highlights a same concept: dumb people outbreed smart people, because smarter folks tend to care too much about the cost of raising children, the insurance, the fuss, the pain. But dumb people couldn't care less. Just go on have fun and have sex.

Alexander Kotrschal, a postdoctoral fellow at Uppsala University, and his colleagues bred two lines of guppies. Next, he dissected the fish and measured their relative brain size, then selectively bred those with the biggest and the smallest-brained fish to create two lines. After two generations the team had two groups of guppies with 10% difference in brain size in females and an 8% difference in males. 

They then taught the fish to count by training them to look for food where a card had either two or four symbols. Kotrschal reported that the large-brained fish seemed to get it, but not the small-brained fish.

Image: humorgraphics.com

Next, they bred the smart and dumb guppies and found out that the dumb fish produced more abundantly than the smart ones. The small-brained fish averaged seven offspring in their first brood whereas the large-brained fish had only six. Also, they discovered a difference in terms of gut size between the fish--the guts of the small-brained fish weighed 5.5 milligrams compared with just 4 milligrams for the large-brained fish. 

That primates have fewer offspring compared to other mammals and humans have fewer still, may be a consequence of the bigger brains, Kotrschal suggested. 
It makes perfect sense because large brains are hard to maintain. Although the human brain accounts for less than 2% of a person's weight, it consumes 20% of the body's energy. A creature with larger brain could rely on its intelligence to survive, whereas a smaller-brained creature would have to rely on physical strength, or reproduce abundantly to ensure the survival of its species.

Image: ikekarin.blogspot.com

Nevertheless, there are still questions to be answered. Six offspring versus seven offspring is quite insignificant, and that can be attributed to noise. The same goes to the gut size. Moreover, the researcher reported that the large-brained fish seemed to get it. Seemed. Need I say more?

So if you have to choose between having high intelligence or abundant offspring, which would you choose?


Malcolm
info: http://news.sciencemag.org/sciencenow/2012/07/bad-news-for-big-brains.html?buffer_share=b4246&ref=hp