Charles Darwin's theory of "sexual selection"—that females of a species choose to mate with males having the best genes—has been held up as a fundamental pillar of evolution in classrooms and science texts for well over a century. Many generations of students have been taught that this is the way evolution works.
After all, from an evolutionary standpoint, it makes perfect sense—females should mate with the highest-quality males of their species to best ensure the survival of their offspring, and this leads to ever-stronger, ever-smarter, ever-improving members of the species, driving the process of evolution ever onward.
There's just one problem: It's not true. Researchers have proved that while the theory may sound good, things don't work that way in real life.
The Wall Street Journal, in a May 5 article titled "Darwin Revisited: Females Don't Always Go for Hottest Mate," summarizes findings from some research projects designed to test Darwin 's hypothesis.
In a 24-year study spanning multiple generations of collared flycatchers (a bird species), Swedish researchers found that females who mated with prime-quality males ended up with fewer and less-attractive offspring. The reason? "The studs were so busy mating they had no time to raise offspring, causing their health and fecundity to suffer. Homelier birds were better dads, raising sons who had more mating success."
In other words, the results were the opposite of what evolutionary theory would have predicted.
Crickets are another notable exception to Darwin 's theory. Female crickets mate with nearly any male, making no attempt to choose the "best" available. In so doing, "they increase the genetic diversity of their offspring, improving the chances that some will survive no matter what pathogens and enemies the kids encounter."
The Wall Street Journal article also points out that "other females are not as enamored of sexy traits as [the] theory claims. While big-antlered red deer are busy fighting each other to show a female who has the best rack, the doe sneaks off to mate with less well-endowed stags. Female red-winged blackbirds are not easily impressed, either. Having the most macho plumage has no detectable effect on how many offspring a male sires."
The article cites Stanford University biologist Joan Roughgarden as saying: "In a number of species, reproductive behavior does not conform to Darwin 's theory of sexual selection. The idea that females choose the genetically best males is wrong. Instead of choosing mates who will increase the genetic quality of their offspring, females make choices that will increase their number of offspring."
The article also highlights a significant problem with Darwin's ideas about sexual selection—namely, "it fails to explain the persistence of, shall we say, homely males." In other words, if females do indeed choose to mate with males who have the most genetically desirable attributes, "then after enough generations every peacock should have a tail to die for. But they do not. Every flock has studs and duds."
If you would like to learn more about the seldom-discussed flaws in the theory of evolution, and to discover what the scientific evidence really reveals, be sure to request or download a free copy of our eye-opening booklet Creation or Evolution: Does It Really Matter What You Believe?