Genetic Map of Northern Europe

From The New York Times, another genetic map shows that there are, in fact, genetic differences between the nationalities of Northern Europe, according to a study of Australian individuals of Northern European descent.



Says the Times: "The graphic records two sets of correlations (labelled PC1 and PC2) in the genetic data derived from the various populations." Can I say what that means, exactly? I cannot. But the key takeaway here is that the proximity of any two points on the chart correlate to genetic similarity between individuals. And as you can see from the color-coding, individuals from the same country clearly cluster genetically. There is, though, a fair bit of overlap, except when it comes to the ever-anomalous Finns, who appear to have wandered off the genetic reservation altogether. Indeed, the Finns appear to be suffering the peculiar existential condition of not even being all that genetically similar to themselves. (CEU refers to the general European population, by the way.)

The researchers have drawn some interesting conclusions from their study.

The Australian team says that natural selection has probably helped differentiate the various populations in their survey. Another factor may be that the Irish have inherited more genes from the first settlers of Europe, hunters and gatherers who were followed by people who practiced agriculture, while the Finns may have some ancestors who came from East Asia.

It would be interesting to discover that the Irish have evolved to inhabit a uniquely Irish niche in the ecology of Northern Europe, and the Swedes another distinct niche, etc. That would seem to be to me the consequence of what these researchers say, and I find it surprising; I always figured whatever genetic differences existed between populations were just due to genetic drift. But of course, whatever differences we're talking about aren't very large, anyway. It's not like we're talking about different species or anything.

On the other hand, if you cock your head and look at a Finn in just the right light...

More Human Evolution Maps

Love this graphic from Mike Rosulek. He has a few other designs, too. And they're purchasable - you can buy the t-shirt! He's donating revenues from the sales to the NCSE, which is committed to "defending the teaching of evolution in public schools." Of course, if you're a creationist, you might try something else... maybe a portrait of Jesus Christ with the title "Maverick"? Hmm, that could probably sell, come to think of it. Maybe I ought to open a Zazzle account...

Anyways, to the maps. These again come from from the Washington Post via Kelso's Corner: a graphic, put together by Patterson Clark, recounting some of the changes in the human genotype over the past few thousand years. It ran on Darwin's birthday, according to KC, though this might be an intricate deception as I can't actually find the link at the Post's website. Regardless, the maps are pretty interesting.









There's more at Kelso's Corner, including a map showing the evolution of lactose tolerance.

Human Migration

I like this map of the spread of humans across the planet.



The projection (some kind of oblique mercator?) [UPDATE: it's a Dymaxion map, apparently.] makes the course of human migration seem like the natural consequence of the spatial relationships between the continents - which of course is just what it was. (It also makes the hypothesized route to North America actually seem like easily the most sensible way to get from Europe to the New World, though I don't know what that dashed line is indicating; it seems to be suggesting that Europeans were emigrating to eastern Greenland during the Stone Age, but I've never heard of such a thing.)

The blue hatchmarked lines indicate the extent of ice and tundra during the last ice age. The numbers are thousand of years before the present, and the corresponding colored arcs on the map indicate the spread of humans at those times. According to this map, migration was most rapid through ice-free southern Asia. People actually arrived in Australia before they ever made it to Europe, which climatically was not nearly as rosy as it is today. It took still longer to make it to northeastern Asia, and then the Western Hemisphere was the last area to become populated when a land bridge allowed people to cross over from Asia.

The letters indicate mitochondrial DNA haplogroups. If they mean something to you, then bully. If not, I'm afraid I'm not qualified to explain them. I do like the map's pretty colors, though.

The Genetic Map of Europe

Speaking of genetic variation in Europe, this map by Manfred Kayser and others is fascinating.



It's a bit hard to read at first. (You can click on it to see a bigger version.) The basic idea is to show the genetic relationships between 23 distinct populations across Europe, which are physically located as indicated on the right. So the more populations overlap, or the closer they are to each other, the more genetically similar they are.

The genetic map is also configured to roughly correspond to the physical relationships between the populations. One thing you can see is that they are more spread out along the top-bottom axis than along the left-right axis. That means there's greater genetic variation between north and south than there is between east and west.

The fascinating thing is how the history of Europe can be read in these patterns. From the New York Times write-up of the paper:

Europe has been colonized three times in the distant past, always from the south. Some 45,000 years ago the first modern humans entered Europe from the south. The glaciers returned around 20,000 years ago and the second colonization occurred about 17,000 years ago by people returning from southern refuges. The third invasion was that of farmers bringing the new agricultural technology from the Near East around 10,000 years ago.

The pattern of genetic differences among present day Europeans probably reflects the impact of these three ancient migrations, Dr. Kayser said.

It makes sense that latitudinal genetic variation would be greater than longitudinal variation. People accustomed to a certain climate - especially farmers - would be more likely to spread quickly along east-west lines, since places that have similar latitudes tend to have similar climates; people who are adapted to live at a given location are more likely to be comfortable 500 miles due east or west of that location than 500 miles due north or south. So it would take longer for populations to spread north or south, which would allow more time for genetic changes to emerge.

There are the Alps, too, of course. They run generally east-west, and serve to partially block the Italian peninsula from the rest of Europe. This relative isolation is probably why the Italian populations are among the most genetically peripheral in Europe.

And then there are the Finns. They don't even genetically overlap with other groups in the study, according the metric the authors are using - in fact, they're not even close; they're way off by themselves in the upper right-hand corner. According to the NYT, the genetic barrier between the Finns and the rest of Europe "arose because the Finnish population was at one time very small and then expanded, bearing the atypical genetics of its few founders."

The Lactose Tolerance Map of Europe

More European genetics! This was published in Nature. Don't worry about the top map. The middle one shows genetic diversity in the milk-producing genes of European cattle. The bottom one shows the geographic distribution of lactose tolerance in Europe. Darker shades of orange indicate greater diversity.

So why is this so interesting? Because the high level of genetic diversity in north-central European cattle is an indication that that's where cattle have been around the longest: that's the area where their genes have had the most time to diversify, like an old tree whose branches have had a lot of time to spread out. And see that dashed black line in the bottom map? That indicates the area where the fossil record shows that people have been herding cattle the longest. So the genetic record and the archaeological record really strongly agree: cattle have been around for a long time in north-central Europe and southern Scandinavia.

Now look at the bottom map - the one that shows lactose tolerance in the human population. Of course, all humans digest milk as babies. But it's only thanks to some relatively new genes that many of us are able to digest milk as adults. These are the genes that make us lactose tolerant. And where are those genes concentrated? In almost the exact same area as the oldest European cattle! In other words, Europeans have evolved to be able to drink milk in just those areas where that adaptation has been most advantageous.

Those original cattle herders - the Funnel Beaker culture - established themselves aroundd 5,000 to 6,000 years ago. So, as with skin color, we're not talking about a real long time in which these evolutionary changes have occurred. Nonetheless, the population today in The Netherlands and Sweden is more than 99% lactose tolerant.

Europe isn't even the only place lactose tolerance evolved. It's happened even more recently in Africa, among three distinct populations in Kenya and Tanzania, as well as Sudan, and as recently as 2,700 years ago. (No word on lactose tolerance in India, but given that they eat a lot of dairy and have had domesticated cows the longest, there's probably some interesting genetic history there as well.)

The Blue Eyes Map of Europe

And here is a map of the distribution of fair eyes in Europe.



It's a very - though not entirely - similar distribution to that of blonde hair. The concentration of these really sort of strange traits around the Baltic makes you realize that northern Europeans, and especially Swedes and Finns, are kind of a race of mutants. Not that there's anything wrong with that. But it makes you wonder why these adaptations never showed up on a large scale in northern Asia and northern North America. Those areas were certainly populated long enough for such traits to take root.

The Blonde Hair Map

Apropos the last post, here is a map of the distribution of blonde hair across Europe, via Strange Maps.



Any guesses as to where the "blonde gene" first cropped up?

By the way, I don't want to sully the Vikings' good name by implying that they may have been engaged in any lascivious behavior during their various rampages across Europe, but it's interesting to compare the blonde map with this map of Viking invasions.

The Skin Color Map

Do this, says NPR's Robert Krulwich:

point your elbow to the ceiling.

Then imagine yourself naked.

Then look at the patch of skin on the inside of your upper arm, the part of you that almost never sees the sun.

Whatever color you see there is what experts call your basic skin color, according to professor Nina Jablonski, head of the Penn State Department of Anthropology.

This map shows skin colors across the globe - the average colors that indigenous people would see if they did the upper arm test:



Humans tend to evolve towards lighter skin when they move toward the poles, and towards darker skin when they move towards the equator. Obviously, the process takes many generations - but apparently not as many generations as once thought:

Skin has changed color in human lineages much faster than scientists had previously supposed, even without intermarriage, Jablonski says. Recent developments in comparative genomics allow scientists to sample the DNA in modern humans.

By creating genetic "clocks," scientists can make fairly careful guesses about when particular groups became the color they are today. And with the help of paleontologists and anthropologists, scientists can go further: They can wind the clock back and see what colors these populations were going back tens of thousands of years, says Jablonski.

She says that for many families on the planet, if we look back only 100 or 200 generations (that's as few as 2,500 years), "almost all of us were in a different place and we had a different color."

That's kind of amazing. That's like going from black to white in the time between Socrates and ourselves. Evolutionarily? That's really fast. (It's interesting that every new finding about human evolutionary change seems to point towards it occurring faster than previously thought.)

Here's the link to the audio of the NPR story. Thanks to loyal reader camella and&also& kt for the tip.