Old men shagging young birds

Kristen Hawkes of the University of Utah, after studying the Hadza hunter-gatherers of Tanzania, has proposed that grandmothers must have played an important role in the ascent of Homo sapiens. \”Good foraging grannies mean healthy Hadza kids – and that was also true for our ancestors,\” she said.

Hawkes argues that when our apeman ancestors were evolving in Africa, females normally died at child-bearing age. Then an occasional female lived a little longer, and would have helped her daughters, when they had their own children, to dig and forage for food. These grandmother-mother pairings thrived, so their genes for longevity would have been passed on. In this way, the slow rise of the senior citizens began.

But now Caspari has extended the idea. It wasn\’t granny power on its own that did it; grandfathers played a critical role,

Indeed, as other researchers have pointed out.

Just as grannies helping grand kids to survive will tend to perpetuate the genes for long lives, so will those of the age of grandads covering those of the age of their children do so.

For one of the things about human beings is that we\’re long lived for our size. It\’s not a hard and fast rule, but there\’s a general relationship between size of organism (mammals have a different relationship from reptiles, etc, but the relationship generally holds within each major design of animal) and length of life.

Some have even compared it to the number of heartbeats in a life: shrews have very fast heartbeats, elephants very slow, but not all that different a number of total heartbeats in an average lifespan. And yes, heartbeat is associated with size.

When plotting this relationship humans are way, way, off the trend. Much longer lives than would be expected for our mass/heartbeat.

And one of the reasons is that grandads chased the teenage girls, thus passing on those genes for long lives.

At the extreme it\’s been said that every human over 50 owes their existence to dirty old men. An exaggeration, yes, but one with that vital grain of truth in it.

9 comments on “Old men shagging young birds

  1. Tim, are you approaching your 50th birthday by any chance?

    Anyway isn’t the problem with that idea that you’d expect men to live much longer than women if that were case?

  2. Only if the longevity genes are gender specific, which they almost certainly wouldn’t be. There’s not that much room on the solitary sex determinant chromosome, and no reason for genes relating to cell repair etc to be there.

  3. Ian, as I understand it traits that only really benefit one sex tend to become specific to that sex if the impose even a slight reproductive cost on the other sex.

    Living for 40 years beyond your reproductive peak would seem to fall into that category.

  4. It depends on the arrangement of the chromosomes and DNA. Seems often people doing calculations and reasoning with evolutionary theory forget that. Evolution has to work with how things are.

    It might be an ideal design to be sex specific with every trait, but the DNA can’t do that most of the time, because it would be too great a rearrangement.

    Old ladies living longer doesn’t actually put any reproductive cost on females even if it isn’t any benefit, and it probably is anyway. But even if not, you can always kick them out to starve to death. The old chieftain getting fourteen year olds up the duff benefits his genes, and that’s what matters.

  5. My girlfriend breeds rats (which are the opposite outlier to humans on that mass-heartrate/longevity graph), and she’s been doing this for years. The best of the boys are bred for as long as they can handle it, but the girls retire well before menopause.

  6. Matthew:

    What drives her to such bizzare behavior? Aren’t you and she sufficiently intimate?

  7. Rats make great pets. They’re like a cross between cats and dogs, but pocket sized. Intelligent little buggers too. I used to teach post-secondary engineering and we’ve had rats with better problem solving skills than 90% of the students.

  8. If old men plus young women was such a good evolutionary idea – why was there a need for the little blue pill to be invented.

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