A few years ago, I was thinking about genetic male morphs. Turns out that you find qualitatively different forms of males in many species: Barry Sinervos’s lizards, Shuster’s isopods, Lank’s ruffs, jack salmon, etc. Logically, the Y chromosome would be the best place for a such a genetic switch, since that would avoid negative side effects in females. The problem is that the Y carries very few genes.
Alternate strategies don’t have to to be as complicated as they are in ruffs or Uta stansburiana. Different levels of aggressiveness, or different points on the cad/dad axis, would have different selective payoffs in different environments. If a new environment favored lower (or higher) aggressiveness in males , a Y-chromosome that induced lower (or higher) aggressiveness would take off. And since different Y chromosomes do indeed affect the level of aggressiveness in mice [which I just found out], possibly by affecting testosterone production – this mechanism is plausible.
This could explain a funny genetic pattern in the domestication of horses. There’s a fair amount of diversity in horse mtDNA: it looks as if many different mares were domesticated. On the other hand, it looks as if only one stallion was ever domesticated. All living stallions today are his descendants.
Stallions are pretty aggressive, and must have been hard to tame. Maybe one was genetically unusual – wimpier. Tameable.
Fortunately for all concerned, the selective value of aggressiveness, etc. has been the same for all human populations forever and ever, before and after the development of agriculture. Otherwise you might see weirdly rapid expansions of particular Y-chromosome haplogroups – common, yet only a few thousand years old.
West Hunter 
I wonder what explains the unusual evolutionary history of the spotted hyena. Here the tables are reversed – the female is the dominant sex, and is physically more robust than the male, with higher levels of testosterone.
“Fortunately for all concerned, the selective value of aggressiveness, etc. has been the same for all human populations forever and ever, before and after the development of agriculture. Otherwise you might see weirdly rapid expansions of particular Y-chromosome haplogroups – common, yet only a few thousand years old.”
I did a double take when I read this. Maybe you should invest in a special font for sarcasm.
A special font! He still uses bracketing underscores for emphasis;)
I used to do that, too, but the latest update to my android keyboard makes that cumbersome. (FTR, I publish most of my comments via smartphone — and yes, even the long, meandering rants that nobody bothers to read.) *This* is more convenient.
It’s been done.
http://sartalics.com/
http://en.wikipedia.org/wiki/Irony_punctuation
See also:
http://mentalfloss.com/article/12710/13-little-known-punctuation-marks-we-should-be-using
I knew that. 🙂
It seems plausible that a good deal of aggression would still be needed by early farmers to fight off mobile raiders. Would an ability to plan in the long term and a desire to stay rooted in one place not be the most important psychological traits? (I don’t deny some reduction in aggression, but I suspect this would come more with later state pacification, as Peter Frost has been pushing recently.)
Perhaps specialization is more effective in that environment? Get the farmers to form a defensive shield wall which the centurions / huscarls / knights etc use as a base to do all the actual killing?
That plan falls apart when the huscarls chase the retreating Normans down the hill because they’re too dumb to contain their aggression.
Verbal aggressiveness?
I wonder if there exists an environment where small-scale farming, sufficient to feed their offspring, is possible by females with the result that males need not cooperate much and thus aggressiveness is not selected against?
I am having trouble thinking of such an environment.
The Bantu Expansion is exactly what you are looking for.
(Or, more generally, the demic diffusion of west African speakers of Niger-Congo languages upon the advent of agriculture and iron tools.)
Looks like another example of a special font needed.
it looks as if only one stallion was ever domesticated. All living stallions today are his descendants.
Maybe the other domesticated stallions shot blanks? Or fathered only mare foals.
I wonder what cattle look like in this regard?
Wonder if any of the admixed New World provide any good test cases for this in humans. Aframs tend have lots of European y-dna groups, in excess of their autosomal European percentage.
This also brings to mind Diamond’s GG&S contention that zebras were just too damned mean to domesticate – maybe they didn’t try hard enough to find that one cooperative stallion.
I figure all that was necessary was the line descended from the ur-stallion was noticeably easier to work with. Even if you did domesticate other males, their direct male descendants would be bred less often and would die out.
Zebras aren’t that hard to break. Jared Diamond was wrong.
About a lot of things.
I though that GG&S was quite good, from what I remember and my limited knowledge of the field….But there is a flaw in the narrative iirc:
He explain a lot of broad historical (and pre-historical) tendencies from geographical, ecological and pathogens differences, with the subtext of those beeing enough to explain different histories and technical achievements without relying on human biology.
But on the other hand, it prove those local differences are really significant (and made more so given the difference in technolgies it induced) on a timescale relevant to evolution (as proven by the change in domesticated crops and animals)…so it has to induce biological differences in humans too, even if there was none in the first place…
The British Army started to tame zebras because they had resistance to the tsetse fly but then someone developed a vaccine for horses so they didn’t bother.
Awesome photo. I’d bet that if the British had fielded zebra mounted cavalry in 1916, the battle of the Somme would have been the end of WW1.
For us idiots in the crowd: is there any such an oddly successful y haplogroup?
http://en.wikipedia.org/wiki/Haplogroup_R1b_(Y-DNA) especially some of the sub-clades
plus Mongols, Arabs, Bantu expansion etc
I recall reading that European colonists were able to domesticate elands and use them as milk producers. North Africans and Asians were able to domesticate elephants to some extent. Although the Asian elephant is different from the African elephant it is still a pretty big, potentionally very dangerous wild animal.
It is certainly odd that although Sub-Saharan Africa has an enormous diversity of large mammals supposedly none were suitable for domestication.
It is certainly odd that although Sub-Saharan Africa has an enormous diversity of large mammals supposedly none were suitable for domestication.
Or perhaps the human populations were not suitable domesticators. And modern humanity has not seen fit to domesticate anything new except for the Siberian fox project.
Yeah, how long do I have to wait for pet koalas?
To further support your ideas that domestication of horses is tied to the sex chromosomes is the large difference in a number of traits between a mule, male donkey and female horse, and a hinnie, female donkey and male horse. No less an expert on mules and hinnies than George Washington, who helped to introduce the mule to american agriculture, had a lot of positive things to say about mules and some terrible things to say about hinnies. It is harder to breed a hinnie than a mule for reasons that aren’t too important to this thread but what is interesting is that the sex of the parent of a horse-donkey combination makes such a large difference in how usefully domesticated the animal can be. A hinnie George Washington said will carry a grudge for years and then one day when it is least expected will viciously kick its owner. The mule on the other hand became a tremendously useful work animal, much used and desired by farmers even though it could not reproduce.
Professor Dude, don’t try to steal our band name. That would be bogus. Your blog is excellent BTW.
Catch you later!
Once one has a fair number of domesticated animals it is probably easier to produce new varieties for different purposes by selective breeding rather than start at the beginning again with a totally wild species.
The San Diego Zoo has a pen about a 100 yards long for the wild Przewalski’s horses of Central Asia. They are memorably aggressive — constantly snapping at each other and bolting the length of the enclosure.
I’ve sometimes wondered who was the first human to ride a horse. I suspect he’d be a skateboarder today: probably a wiry 17-year-old boy absolutely lacking in fear.
Yes, if not younger. IIRC in the Hungarian uprising it was the 13-14 year old’s with no sense of mortality who were noted as the bravest at taking on tanks with firebombs.
I read a paper once that claimed that Neanderthal remains showed evidence of rodeo-rider-type injuries because Neanderthals must have jumped on the backs of large animals to kill them, a bit the way that lions do with cape buffalo. They ate horses too (much like the modern Brits).
I’m not suggesting that Neanderthals domesticated horses, but it suggests a model for how it might have happened – when it turns out to be more fun to ride it than kill it, maybe you want to keep the fun going.
My opinion on almost all domesticates, is that they were self-domesticated – with the exception of cats, which aren’t domesticated.
I saw an interesting documentary on Moose in Alaska and people were wondering why so many moose got killed on highways, especially moose calves, when you’d imagine that it would be safer to stay away from highways and moose cows would know this.
Turns out that bears are the main predators of moose and especially moose calves, and a moose cow near birth actually had a preference for calving just a few yards from the highway because bears were afraid of the highway – due to it being associated with hunters – and wouldn’t dare get that close!
So, I see a domestication scenario playing out as follows:
1. Due to food shortages, or living in marginal hilly land, people learn to plant and tend to some staples – emmer wheat or eincorn.
2. Eincorn/Emmer wheat attracts goat/sheep, pigs, cattle, horse to swoop by and raid.
3. Only the tamest stuck around, as they:
a. Could tolerate humans
b. Were enough of a threat to be killed
3. Obviously wild horses and wild cattle (Aurochsen) are far too dangerous to have near a small settlement, so they would have been driven off initially, but sheep/goats are smaller and easier to manage and would be the first domesticates
4. Once you have domesticated sheep/goats, they are usually moved from their natural hilly habitat to the lowlands, and protected by humans will destroy all trees and shrubbery in sight, and effectively create forest clearances, thus enabling larger settlement and more farming
5. Larger settlements, allow cattle and horses to graze on the margins, just far enough from humans. But if like the moose, staying close to human settlements deters bears and/or wolves, then over generations you will get horses and cattle that depend on humans for protection from their natural enemies, and so they domesticate themselves.
Sandgroper
“That plan falls apart when the huscarls chase the retreating Normans down the hill because they’re too dumb to contain their aggression.”
The huscarls didn’t chase the retreating Normans. The fyrd (farmers) did.
Off-topic but interesting bit of history, http://en.wikipedia.org/wiki/Varangian_Guard
That makes more sense.
So how did Harold’s brothers get killed?
Dunno, probably took an arrow in the knee 🙂
“On the other hand, it looks as if only one stallion was ever domesticated.” That is not quite a fair inference to make: it is certainly possible that other stallions were domesticated, but due to either selection or chance, their Y chromosome lines died out. Still, the main point stands that something about this stallion’s Y chromosome is surely the reason all domesticated stallions descend from him, and this something probably consists of alleles on the Y chromosome related to aggression (or lack thereof). Also, is there a reason Greg rarely links to the papers I presume he is referring to? The ‘Equine Adam’ paper being this one: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0060015
Regarding recent expansions of human Y haplogroups: what are the likely selective forces? Agriculture makes aggression an obvious choice (farmers domesticate their own societies almost like they domesticate horses, etc.), but I would imagine genes relating to male germ cell development, spermatogenesis, etc. could be candidates for recent selection as well. Most of the NRY genes I can think of are related to sperm production: USP9Y, AZF1, BPY2, DAZ1, and so on. Related question: does the lack of recombination in the NRY make sleuthing out individual genes under recent selection impossible, or merely very difficult?
“Regarding recent expansions of human Y haplogroups: what are the likely selective forces?”
Mobility might be a neccessary if not sufficient condition. Also if pastoralism tends to create a raiding culture most of the time and raiding cultures select for aggression you could get both mobility and aggression if a population took up pastoralism from scratch.
Also once created an aggressive, mobile pastoralist population held back by a barrier of some kind might expand rapidly any time that barrier lowered.
Probably other possibilities also.
Ah, I now see that Greg already covered my first point above: “I figure all that was necessary was the line descended from the ur-stallion was noticeably easier to work with. Even if you did domesticate other males, their direct male descendants would be bred less often and would die out.” My apologies for not reading the comments section prior to commenting myself.
“Everything is different, but the same… things are more moderner than before… bigger, and yet smaller… it’s computers… San Dimas High School football rules!”
Pingback: linkfest – 04/07/13 | hbd* chick
@Discard
“Awesome photo. I’d bet that if the British had fielded zebra mounted cavalry in 1916, the battle of the Somme would have been the end of WW1.”
Yeah it is. Zebra cavalry would be cool in a steampunk setting – along with rhino cavalry.
BTW, it’s pronounced: Zeb-rah
Pingback: arab thoroughbreds | hbd* chick
“I wonder what explains the unusual evolutionary history of the spotted hyena. Here the tables are reversed – the female is the dominant sex, and is physically more robust than the male, with higher levels of testosterone.”
There is a paper comparing the T differences between hyenas and bonobos, both of which have a matriarchal structure. iirc bonobo males have lower T than chimp males but the female levels are the same. There is also some difference between the two with testosterone and cortisol secretions.
and then there was this, though a bit suspect:
“High up in the hills above the University of California at Berkley is the world’s largest colony of spotted hyenas, massive bone-crunching beasts who fight with each other for the chance to have their ears scratched by Laurence Frank, the zoologist who brought them over as infants from Kenya. Various scientists are studying their sex-reversal system. The female hyenas are bigger and more muscular than the males and have the same weirdo genitals ands elevated androgen levels that their female cousins do back in the savannah. Everything is in place except … the social system is completely different from that in the wild. Despite being stoked on androgens, there is a very significant delay in the time it takes for the females to begin socially dominating the males- they’re growing up without the established social system to learn from. “