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January 16, 2010 12:00 AM   Subscribe

Indeed, at 6 million years of separation, the difference in [Y-chromosome] gene content in chimpanzee and human is more comparable to the difference in autosomal gene content in chicken and human, at 310 million years of separation.
It is commonly said that the Human and Chimpanzee genomes share 99% or more identical DNA. In a surprising development about to be published in Nature, the Y-chromosomes of these two species were found to share only 70% of their DNA, raising important questions about the mode and tempo by which speciation from a common ancestor occurred. This finding may point the finger at the evolution of different patterns of sperm-competition and mating practices within these two species.
posted by Rumple (21 comments total) 10 users marked this as a favorite
On one hand, this is fascinating.

On the other hand, this is material for so many bad jokes.
posted by rodgerd at 12:44 AM on January 16, 2010 [1 favorite]

So is this fantastically weird because it is between Chimpanzees and Humans, or that it occurs between two otherwise highly related species?
posted by selenized at 12:47 AM on January 16, 2010

It's fantastically weird because the sex-specifity has taken people by surprise. The (not doubt hotly-debated and heavily politicised) question will be to what degree the relevant genetic material is uninteresting or to what degree it suggests the species differences between us and other primates are driven by MSY specfic mutations.
posted by rodgerd at 12:51 AM on January 16, 2010

So...good news for men who don't want to be like their fathers?
posted by clockzero at 12:53 AM on January 16, 2010 [1 favorite]

Very interesting. I wonder how this new research will affect the old canard that humans share 50% of their genes with a banana (which reminded me of a related AskMe question).
posted by amyms at 12:56 AM on January 16, 2010

In other Y-Chromosome news, Most men in Argentina (94.1%) have a european Y-Chromosome. But a majority (53.7%) have native American mitochondrial DNA (inherited from the mother).

I think we can all figure out what happened there.


But the chimp thing. I have no idea what that's supposed to imply. I thought the Y chromosome didn't have many actual active genes on it.
posted by delmoi at 12:57 AM on January 16, 2010

(er, I should say a majority of people have Native American mtDNA. Only men have Y-Chromosomes, of course)
posted by delmoi at 12:58 AM on January 16, 2010

The lab I work in is collaborating with a researcher in the Eichler lab who is working on a similar kind of project, looking at the evolution of duplications of portions of a gene family called morpheus, from more distant primates like baboons to gorillas, up to chimps and humans.

Our lab is looking at the chromatin structure — how the DNA are bundled up — to determine if and how these duplications behave differently along the evolutionary timeline.

If this chromatin structure changes, different chunks of DNA open up and change how genes are regulated, how they are turned on and off. For example, in baboons, these genes may be switched on or accessible in the testes, but in no other tissue, while the genes are increasingly accessible in other primary tissues (brain, heart, skin, etc.) in higher primates.

This region has been selected for as humans evolved. Some genes in this family are associated with sperm production and immune system proteins. It will be interesting to see if there is any association with regulation of or proteins related to brain functions, such as language.
posted by Blazecock Pileon at 1:19 AM on January 16, 2010 [3 favorites]

This is fascinating - but it's such a radical reversal of a lot of existing thinking that I know already anyone I tell about it will just assume I'm confused or ill-informed.
posted by Phanx at 1:48 AM on January 16, 2010

... humans share 50% of their genes with a banana ...

Well, human males, anyway ...
posted by bwg at 2:16 AM on January 16, 2010 [1 favorite]

More freaky science news Scientists have long been genetically modifying organisms to emit light at certain times in order to measure gene expression.

But recently scientist actually genetically modified a mouse brain to add photo receptors inside the brain. This lets them directly and non-destructively deactivate neurons directly with a laser, rather then an electrode or generating a lesion. How fucking crazy is that?
posted by delmoi at 2:59 AM on January 16, 2010 [2 favorites]

Does this mean Valerie Solanas was right?
posted by chillmost at 3:11 AM on January 16, 2010 [1 favorite]

On the other hand, this is material for so many bad jokes.

But the people who'd make them don't follow science news, hopefully. Or at least someone will remind them we have 46 chromosomes etc.
posted by ersatz at 4:26 AM on January 16, 2010

This reminds me of a comment in Steve Jones' Why creationism is wrong and evolution is right lecture: "The key to what makes us human may lie as much in our scrotum as in our skull".

(NB. I have heard this lecture on three separate occasions, with slightly differences. I can't be sure whether he says this in the video from the Royal Society)

delmoi: optogenetics is quite an important new technique in neuroscience. As well as looking at gene expression (which is what fluorescent proteins like GFP and the like were originally used for in the lab), it is possible to make optical sensors for voltage, intracellular calcium-ion concentration, and cAMP concentration. The photoactuators can do more than just deactivate neurons: they are ion channels of various kinds, and can be either excitatory or inhibitory. Halorhodopsins (light-activated Cl- pumps) are inhibitory, whereas channelrhodopsins (light-activated cation pumps) are excitatory.
There was a good review in Science: The Optogenetic Catechism
posted by James Scott-Brown at 4:45 AM on January 16, 2010 [1 favorite]

Hah! So importance of sperm competition once again raises its head, so to speak, after being pooh-poohed in these pages and elsewhere. You can't deny that Robin Baker's ideas of "Sperm Wars" have a powerful explanatory power. They resonate strongly with me, at least on a literary level.
posted by Faze at 4:56 AM on January 16, 2010

I'd like to see the comparison done against bonobos. If sexual competition and sexual selection is making the difference, we might see a similar different between chimps and their closest genetic cousins.
posted by clvrmnky at 6:07 AM on January 16, 2010 [2 favorites]

Sequencing and assembling the whole genome of a vertebrate is an expensive task, despite the improvements in sequencing technology that have made it much cheaper. In order to sequence the genomes of more species, people have been taking a number of shortcuts when sequencing them, doing things like sequencing them to only 2× coverage (the gold standard is 10×), not sequencing the Y chromosome, and skipping the extensive genetic mapping done initially for the human genome. The idea is that we can then rely on the homology of the other genomes to the highly studied human genome in order to assemble things in the right order and annotate them.

The problem is that, as shown in this study, some of the most interesting parts of another species's genome are those parts that are not homologous to the human genome, and by using a human-genome–centered approach, all of that gets thrown out.
posted by grouse at 7:55 AM on January 16, 2010

Sorry, guys. It was $1 a tequila shot night at the Zoo Bar in D.C., and, well, the zoo was literally quite next door, and . . . .
posted by John of Michigan at 8:54 AM on January 16, 2010

We're selecting you guys!!! This is fascinating and suggests to me an even greater role for female choice in human evolution. It doesn't seem to me that this would just be sperm competition-- although that clearly seems to be part of it-- but it seems that male competition for females in general is implicated.

So the shape of human nature appears to have been determined by what women like in men at least as much as by what men like in women if not more, which is pretty interesting. Darwin had already suggested an important role of female choice in evolution (peacock's tale and all that) but this, at least from what I can see here, seems to emphasize it even further, whether it's taking place via sperm competition or via competition to have a chance at sperm competition in the first place...
posted by Maias at 3:24 PM on January 16, 2010

On one end, the Y chromosome has around 200 genes, and has a lot of heterochromatin.

On the other end, the X chromosome has around 1400 genes, and not a whole lot of repetitive DNA.

On the other end, the one sticking through the fourth dimension, there is the lyonization of one of the X chromosomes.

Does that even things up?
posted by francesca too at 6:15 PM on January 16, 2010

Considering that the asymmetric methods of reproduction have motivated nature to lump the grand majority of selection pressure onto the males of a species (for an extremely visible example of this, see every species of bird on the planet), it makes a lot of sense that the Y chromosome has diverged from our closest relatives a lot faster than the rest of our genome.
posted by Bobicus at 8:37 AM on January 17, 2010

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