Obsidian Wings

Humans never migrated out of Africa

by Doctor Science

Carl Zimmer is a great science writer I've been following for years. It's not really his fault that his latest NY Times article on human evolution was the last straw for me, finally breaking my ability to quietly tolerate a particular turn of phrase.

The headline for Zimmer's article is: "A Single Migration From Africa Populated the World, Studies Find".

No. Homo sapiens never "migrated" out of Africa. We did not "trek", "emerge", "exodus", or "journey", either. All such travel-based metaphors misrepresent human evolution, and get both the general public and paleoanthropologists themselves into bad mental habits. These metaphors are also (I believe) racist, which is an even worse mental habit.

What Zimmer and the scientists he profiles are calling "migration" is really range expansion. Other animals (and plants) do this all the time, it's not anything unique to humans.

For instance, the Coyote used to be found only on the Great Plains, but since the end of the 19th century its range has expanded to cover most of North America:

Progression of coyote range expansion throughout North America and Mexico

Another example is the Cattle Egret. Native to Africa and the Mediterranean, birds that landed in South America accidentally established a population in the early 20th century, and have expanded to all cattle-ranching areas of the Western Hemisphere today:

Range expansion of the cattle egret

Range expansion is an important area of ecology and evolutionary studies, the topic of a great deal of past and ongoing research. So why don't we use those words when we're talking about humans? Why don't even scientists do so?

One reason, I think, is romantic reification. There's a very long-standing custom of talking about human evolution and history as though it's about a single figure or character, Man. The Ascent of Man, Man Discovers Fire, Evolution of Man, etc. Man is a very active and even heroic character, he Does Things. "Range expansion" sounds dull and even passive; Man is special: he conquers, colonizes, treks. Man also has feelings and goals not shared by mere coyotes or herons, so you get article titles like Population genetics: A map of human wanderlust -- as though human range expansion is driven by emotions, unlike that of mere animals.

But romanticism is only part of it. I think another driver of these sloppy metaphors is racism: specifically, a deep reluctance to accept that humans are all fundamentally African, that our species is native to Africa and *only* Africa.

I'm not saying that Zimmer, for example, is consciously motivated by racism. But there's a racist framework in the field of human evolution, and it keeps people in the habit of writing (and thinking) in racist ways.

Humans never left Africa, any more than Cattle Egrets did. The ranges of the Cattle Egret and Homo sapiens have expanded to cover very large areas outside of Africa, but their African populations are still there.

When Zimmer writes:

People everywhere descend from a single migration of early humans from Africa ... Why leave Africa at all? Scientists have found some clues to that mystery, too.

-- the picture he evokes implies that humans, real people, are not found in Africa today, they "left" or "migrated" away.

Zimmer is just following the conventions of the field. For instance, among the associated papers at Nature that he reports on, one talks about

the exodus of Homo sapiens out of Africa and into Eurasia

An "exodus" is a departure: this phrase is literally saying that (real) humans were no longer found in Africa, they had moved to Eurasia. It's only from context that we know that's not what the authors "really mean" -- but it's bad writing, bad science, and a really bad mental habit.

And then, on the sidebar of the Nature article, there's an audio file in which

Adam Levy investigates how new pieces of the puzzle are revealing our ancestors' journey out of Africa

-- as though "our" ancestors are all from non-African populations.

It's possible there's another element besides romanticism and racism: a clash of scientific dialects. My training is in evolutionary biology & ecology, where "migration" means regular, there-and-back-again travels. Creatures appearing in new places is a completely different phenomenon: "dispersal", "range expansion" or "invasion".

It seems that in archaeology & anthropology "migration" covers almost any movement of peoples -- like an archaeology course on Great Migrations, which covers

the Phoenician diaspora, Greek colonization, Roman veteran settlement, the ‘Sea Peoples' and Visigoth invasions ... labor and pastoral mobility, the Assyrian trade diaspora and the ‘port Jews'.

When such social scientists talk about "migration", they often seem to mean events like the Exodus of the Hebrew Bible, where most or all of a community moves from point A to point B in a single generation. Biologists would call this kind of movement a "shift", not a migration, and would expect it to take many generations.

Some scientists are definitely aware how problematic "migration" and other travel-based metaphors are when talking about human evolution. Here's a good example: The great human expansion, by Stanford's Brenna Henn (now at SUNY Stony Brook), Luigi Luca Cavalli-Sforza, and Marcus Feldman. Henn et al. are careful to call the phenomenon they're studying (range) "expansion", and using "migration" only sparingly:

Figure 1: Ancient dispersal patterns of modern humans during the past 100,000 y. This map highlights demic events that began with a source population in southern Africa 60 to 100 kya and conclude with the settlement of South America approximately 12 to 14 kya. Wide arrows indicate major founder events during the demographic expansion into different continental regions. Colored arcs indicate the putative source for each of these founder events. Thin arrows indicate potential migration paths. Many additional migrations occurred during the Holocene

Scientists and (even more important) science writers really need to stop using romantic and racist travel metaphors when talking about human evolution. It's not all that difficult, really: look at your work and ask, "does it sound like I'm saying that African humans aren't as human as people outside of Africa?" If you are, then you'd better change that sentence.

One of the series of Exodus Paintings by Spanish-born New York artist Maria Largo.

I weep for the future - your debate open thread

by Ugh

Fnck this is really happening isn't it?  Trump is going to drop out and say it's all a joke, no?  No?  

Is it good that I went under contract for a house today?  We lost out the last two times to people with more money than sense.  And here I thought nobody had more money and less sense than I, maybe the Kardashians bought those two houses.

Please try to keep your lunch and dinner down tonight.  

Open thread for the debate.

Feh.  

Your Skittles and Blitz Open Thread

by Ugh

Well.  Great week America, great week.  Is it really too much to ask that police body cam footage in shootings be released as a matter of course?  You're not inspiring a lot of confidence there Charlotte. Also, too.  And three.

Separately, I'm beginning to wonder if we will have a permanent 8 member SCOTUS, as I don't see a GOP controlled senate confirming an HRC nominee.  I'm sure this is the Democrats' fault for rejecting Robert Bork and his Mordor-based jurisprudence.

Meanwhile the Patriots keep on winning, so screw you Roger!

Just three days until the first presidential debate.  You're welcome, rest of the world.

Open thread and stuff.

There hasn't been nearly enough freaking out, apparently

by Ugh

I don't know what to think anymore about the reaction to these latest "attacks" in New York/NJ and Minnesota.  CNN is running large font, all caps headlines like "MANHUNT" and now "CAPTURED" on its front page.  There is the lovely fascistic style of referring to these as "attacks on American soil" and the "Homeland," since the jingoism in the current political campaign is inadequate, I guess.  If only there were more security and spying and profiling and less political correctness and "fighting with one hand tied behind our back" all this would stop.  Right.

And of course Trump is playing right out of the demagogue handbook, again acting as ISIS's unofficial head recruiter (and American Muslim alienator-in-chief), while also making not-so-vague allusions to violence against Hillary Clinton.  But he's got a secret plan to eliminate ISIS, only to be revealed if we elect him - otherwise he'll just keep it secret.  If only he could get the "carrying a cross" part down we'd have quite something on our hands.  He's got 50 days and is tied in the polls, give him time.  

Vote Hillary, it's important.

UPDATE:  Ah, that's more like it, thanks DC!  

We shall deplore them on the beaches....

by Ugh

I don't know, I keep seeing the NYTimes home page "% chance of winning the election" graphic ticking up for Trump.  A few weeks ago it was a 91% chance that Hillary would win, now it's down to 74% at last look, and recent polls show Trump tied!  I keep thinking at some point there will be klaxons and air raid sirens and emergencies declared and bunkers prepared and panic in the streets.  At a minimum, I would hope the mythical #Nevertrumper beasts will hold their noses and urine and vote for Clinton, you don't have to tell anybody (really!).

Meanwhile, how about a Nats-Cubs NLCS?  Please?  And is a Cubs World Series win worth a Trump Presidency?  Okay probably not - but odds seem equally likely right now.

Also, too, can we start paying NCAA athletes now?

At least football is in full swing.  Starting to edge over into bread and circuses territory though.

Open thread, dude.

UPDATE:  Thank goodness no food is grown in California.

Choose Your Poison

by wj

Sometimes, I get serious cognative dissonance in real time. Right now, my local all news station (KCBS) is saying that "a new national poll shows a dead heat" in the Presidential race. Meanwhile, the Washington Post/Survey Monkey poll, just out today, shows . . . a toss-up in Texas. And in Mississippi! (In addition to Arizona and Georgia. And Ohio, North Carolina, etc., of course.)

So what's happening? Who knows? I guess it's a lesson in why you shouldn't look at a single poll and assume that it has the one true story.