why are Ligers bigger than Lions and Tigers?
from Wikipedia: Liger
It is believed that this is because female lions transmit a growth-inhibiting gene to their descendants to balance the growth-promoting gene transmitted by male lions. (This gene is due to competitive mating strategies in lions.) A male lion needs to be large to successfully defend the pride from other roaming male lions and ( Read more... )
It is believed that this is because female lions transmit a growth-inhibiting gene to their descendants to balance the growth-promoting gene transmitted by male lions. (This gene is due to competitive mating strategies in lions.) A male lion needs to be large to successfully defend the pride from other roaming male lions and ( Read more... )
All evolutionary fitness in measured in ONE WAY: how many times does an individual manage to produce offspring that are going to produce offspring as well: to make good offspring (over the course of a life time) you can either *invest* a lot per individual or have a lot of offspring...
There are big disparities between male and female investment in a single offspring though...
Females invest more resources in an offspring than males do. This is true in many (but not all) species, including (btw) humans. It begins with the egg. This is a big investment and a female has a limited supply, it proceeds with the investment into the organism during development which saps the mothers strength while the father is off cavorting (often not provisioning and providing, particularly not in Lion prides) and *importantly* he is having more offspring while all the female's resources are completely invested in one developing offspring. Small offspring sap less of your resources.
Part of the problem for females is that this mate talked a pretty good game pre-copulation (showed off, or whatever) but did he have quality genes or is this offspring going to be pretty useless? This mystery is where male bravado and showy manes come from... If you can maintain a big stupid tuft of mane then maybe your genes are OK. Maybe that is just a lie though. Mate choice is tough. A female doesn't want to invest too much in this offspring, to save her strength and have more later she silences genes that tend to make the offspring gigantic.
As to the mechanisms of competing genes (or gene silencing/imprinting mechanisms) I doubt that the mechanisms or genes for Lions are known. We don't have the tools to study them. This sort of sexual competition is being studied these days in Mice or Flies and the findings are thought to possibly be extended to other organisms. I am no expert so you could try reading more about it other places:
Google -scholar- for:
Genomic imprinting in mammalian development: a parental tug-of-war.
See yah!
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Exactly. What I call "Darwinian score" is exactly this recursive notion.
This is a big investment and a female has a limited supply
Do females ever run out of eggs?
This mystery is where male bravado and showy manes come from... If you can maintain a big stupid tuft of mane then maybe your genes are OK.
Right. This "handicap" idea and sexual selection in general seems to make our world a lot more interesting: deer antlers, peacock tails, music, etc. High testosterone levels are also a handicap, since it weakens the immune system.
A female doesn't want to invest too much in this offspring, to save her strength and have more later she silences genes that tend to make the offspring gigantic.
Are you suggesting that a mother can choose in which kids to silence those genes?
My point is that the Darwinian score of a mother will be the same as that of her partners. This is obviously true if we assume monogamy. Now, this is still the case if we add a couple to swing with them. By induction, all mating configurations can be found. Oops, scrap that! :-)
ok, I can now see the tug-of-war (escalation):
The more successful males are those who make their kids as big as possible, whereas the females who make many smaller kids may end up being more successful. But this would mean that size is not as important it may have seemed: the mothers "benefits" from each large kid just as much as the father. If we assume that female with smaller kids will breed twice as much (a generous assumption, no?), this means that the average big kid will score less than twice as much as his normal-sized counterpart.
The dynamics of this can be quite complex and confusing, but it's still interesting to see how far we can take our qualitative arguments.
(Btw, in Dutch and German, your initials are pronounced "haha".)
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