Male displays might be communicating more than the message “I’m gorgeous” - they might be saying “I’m healthy and well-fed, my feathers wouldn’t be so nice if I wasn’t capable of looking after myself.” Alternatively, sexually-selected male traits might not be about display at all, but some more direct way of winning the competition for females. The evolution of males can be driven by other forces too. However, I do wonder if show-off males also serve as decoys - diverting the attention of predators away from better-camouflaged females and their young. It serves no other purpose than display - and what it signals is “mate with me and your sons will have a magnificent tail too.” If you’ve ever wondered why the male in so many species is more brightly attired than the female, there’s your answer. This is a positive feedback loop that leads to the evolution of exaggerated features like the peacock’s tail. If their sons are reproductively successful, then a small number of children can turn into a large number of grandchildren and great-grandchildren all carrying copies of the matriarch’s genes - which in Darwinian terms is the main thing.įemales in such species will therefore seek mates with heritable traits that will, in time, make their sons attractive to females. Though they don’t have an immediate opportunity to spread their genes far-and-wide, they might over several generations through their male descendants. Indeed, the conflict of interest between the all-your-eggs-in-one-basket strategy of the female and the scatter-gun tendencies of the male is at a maximum.Įxcept that females do have an evolutionary interest in this set-up. So when it comes to sex, what’s in it for females in species of this kind? Philandering, fly-by-night males who don’t help out with the childcare would appear to be a serious liability. When you’re making one big investment rather than making lots of little bets, diversity isn’t nearly so important. where each female has a small number of offspring - perhaps no more than one or two. Reproducing asexually is like sticking to the same number no matter how many tickets you buy.īut what about species of low fecundity, i.e. Obviously, if you’re going to invest in multiple tickets, then picking different numbers for each one increases your chances of winning. In this analogy, each kid is like a ticket - a gamble that it has the right combination of genes to survive into adulthood and reproduce. To understand why this is so advantageous think of reproduction as if it were a lottery. Furthermore if she mates with several males, that’ll mean even more genetic diversity among a female’s offspring. Half the genes come from each parent, but the particular halves vary from sibling to sibling. Sexually produced offspring, however, are genetically distinct from both parents, and also from one another (with the exception of identical twins, triplets etc). Asexually produced offspring are genetical identical to the parent. To begin with, there’s the fundamental advantage of all sexual reproduction, which is genetic variation. Suggested reading What's the point of sex? Thus occupied, they’re not going to make the best of fathers - so why do females put up with them? Males, with their abundant supply of cheaply produced gametes have an obvious interest in sowing their seed as far-and-wide as they can get away with. The mammals, though, are no better than they ought to be. This is why there are so many avian metaphors for true love. That’s especially true of the birds who tend towards monogamy and, in some cases, lifelong monogamy - as with swans and parrots. Such cooperation between the sexes is observed in many species. The most obvious one is that dad sticks around to help protect and raise his kids. This should be more than enough to guarantee the rapid extinction of a sexually reproductive lineage - unless, that is, sex comes with offsetting advantages. So, in terms of evolutionary ‘ fitness’ sexual reproduction comes with an instant 50% penalty. She passes on all of her genes to her offspring instead of having to share parentage with a male. The latter would appear to be at a huge evolutionary advantage. Still, the fact that asexual reproduction is the exception and not the rule does require explanation.Ĭonsider two females: one reproduces sexually, the other asexually. However, it’s extremely rare which is good news for cocks. Parthenogenesis has even been observed among some birds. Indeed there are some species of fish, amphibians and reptiles composed entirely of females. In many groups, including the vertebrates, there are species that reproduce by parthenogenesis, i.e. But why? After all, there is an alternative: asexual reproduction.
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