Zimmer's thoughts

This Week in Human Evolution
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Posted by Carl Zimmer

I've been in low-blogging mode for a few days as I try to fire off a
few dead-tree articles. But I wanted to write up a quick post to draw
your attention to three very interesting pieces of human evolution in
the news.

1. Modern evolution. A new paper presents the results of a systematic
scan for human genes that have experienced natural selection in the
past few thousand years. An impressive 700 regions turned up. The fact
that humans have been evolving during recorded history is not new. The
ability to digest lactose in milk as an adult, resistance to malaria,
and other traits have long been recognized as having experienced strong
natural selection after the dawn of agriculture. But this new study
certainly sets the standard for all future work in this area, because
it is so thorough. (Gene Expression takes you through the steps. The
original paper is here.) The next logical step would be to add new
populations to the database. The new study compares only three
populations--Yorubans from Nigeria, Chinese and Japanese, and people of
European descent in Utah. I wonder how different the evolutionary
pressures are in other groups. Inuits get no benefit from malaria
resistance, for example. Lactase digestion turns up in people descended
from cattle herders. Are there adaptations for eating rice, cassava, or
blubber?

Adaptations for drinking milk are not the stuff of racial controversy,
but brain genes certainly are. Last year there was quite a hullabaloo
over findings that a couple brain genes were also evolving quickly over
the past few thousand years. The fact that natural selection appeared
to be occurring in those genes in Europeans and Asians generated a fair
amount of commentary that at least had a whiff of racism to it. Those
particular findings seem to dissipate in the new study, perhaps because
it looks at a bigger sample of people. On the other hand, there are
other brain genes that the new study identifies as evolving. Some are
found only in one or two samples, and one is in all three. These
results show no simple pattern that can be exploited for blithe
generalizations. So I expect silence from pundits.

2. The Evolutionary Volume Knob. While working on my Smithsonian
Intimate Guide to Human Origins, I was particularly struck by a
visionary paper published in 1975. Mary King and Alan Wilson argued
that the evolution of humans might have been dominated not by the
emergence of new genes, but by new uses for old genes. At the time,
scientists knew precious little about human DNA. They had yet to
sequence a single human gene.

In Nature today, scientists published a study that investigates their
proposal with all the tools biotechnology has to offer today. The
scientists set up devices known as microarrays that can measure the
activity of genes in cells. They measured the activity of over 1,000
genes in liver cells from four species of primates--humans,
chimpanzees, orangutans, and rhesus monkeys. About sixty percent of the
genes show the same levels of expression in all four species,
suggesting that they have changed little since the common ancestor of
monkeys and apes. But they found 14 genes in humans that buck that
conservative trend, showing significantly higher or lower activity than
in other primates. Interestingly, five of these genes encode proteins
that turn on and off other genes (transcription factors). The authors
note that in studies on closely related fruit flies, transcription
factors don't seem to have evolved very quickly. So it's possible that
the patterns found in the new study offer some clues as to why we
humans are so different from chimpanzees compared to fruit flies
separated by the same amount of evolutionary history.

3. Unethical Paleoanthropology, or the People Who Walk on Their Wrists.
[Update 3/9/06: Please be sure to read my additional remarks at the end
of this section.] This is a weird story, but one worth looking into--if
not for the science, then at least for the scientists. A Turkish
scientist came across a family in a remote village who walk bent over
with their hands on the ground. He claimed that they represented an
evolutionary throwback to our quadrupedal ancestors. Then British
scientists got in on the act, and now there's going to be a documentary
on British television in a week or two. It turns out, however, that the
British scientists may have acted in some pretty unsavory ways, paying
off the family not to talk to other scientists or television crews,
etc. The best coverage I've seen is here. Ignore the cheesy background
design at the site--it's good reporting.

I can't tell from what I've read whether any of these scientists is
really claiming that these people have a genetic mutation reverting
them to our quadrupedal past. If they are, they're nuts. Locomotion is
a fantastically complex feature, and any particular kind of locomotion
is made possible by the size and shape of bones, muscles, and tendons,
along with neural pathways to control them. It's not controlled by some
single gene that can switch back to an ancestral state in a single
family. The evolution of bipedalism took millions of years. The
earliest hominids show some hints of bipedalism six million years ago,
but hominids didn't walk efficiently upright like we do for another
four million years. In that time, a lot of changes, both subtle and
dramatic, occurred.

On the other hand, it is certainly true that unusual families can help
scientists learn a lot about our origins. As I explain in my new book
on human evolution, a family in London carries a mutation to a gene
called FOXP2 that looks to have played a major role in the evolution of
language. But it was not enough for scientists to identify a mutation
in this gene in a family who had trouble talking. They needed to show
that it has precise effects on language-processing regions of the brain
and that it shows signs of having undergone intense natural selection.
Somehow, I don't get the sense that the scientists involved with this
new family are going to take that kind of care. Instead, it looks like
it's turning into a televised freak show.

Update 3/9/06: This morning Nicholas Humphrey, one of the British
scientists involved in this work, sent the following comment:

As a distinguished science journalist, you should know better than
to spread empty gossip about the "unsavory" conduct of the British
scientists involved in studying the Turkish quadrupeds. There is simply
no truth in the allegation that we "paid off" the family not to
collaborate with other researchers.

The BBC film, airing on 17 March, provides a responsible,
intelligent, and enthralling account of the science and the human story
that lies behind it. I am proud to be associated with it.

We have published a preliminary report of our findings at

http://eprints.lse.ac.uk/archive/00000463/

On reflection, I want to retract some of what I wrote about this work
yesterday. The claim that Dr. Humphrey and his colleagues paid the
family not to cooperate with other scientists came not from the family
itself, but from a Turkish scientist named Uner Tan of the University
of Cukarova. Dr. Tan had already been studying the family and invited
the British researchers to join him. I should have made that clear. I
should have also made it clear that Dr. Humphrey rejects the claim.
Both of these points were made in the article I linked to. The
journalist in me looks at the post I wrote yesterday and thinks, "You
really should have gotten confirmation on that." And since going to
Turkey is not really practical for me, I can't verify Dr. Tan's claim.

I decided this morning to take another look the information I did
gather, and nose around a bit more. As Dr. Humphrey mentioned, he has
published a report on his findings, which is available online. It's not
a paper in a peer-reviewed journal, but rather a "discussion paper"
published by the London School of Economics, where Dr. Humphreys is a
professor. It was presented at an LSE meeting in October.

Dr. Humphrey and his co-authors write that Dr. Tan and another
researcher, Osman Demirhan, began studying the family in 2004. Dr. Tan
contacted the British scientists and they visited the family last June.
In the acknowledgments, the authors write, "We are glad to thank Uner
Tan for encouraging us to investigate the family, and for providing
contacts and support, and him and Osman Demirhan for their scientific
comments. Tan and Demirhan were invited to share authorship of this
paper, but this did not prove workable."

The authors also note that they got informed consent for their work, as
did the BBC. They write, "The father of the family signed a statement
in Turkish which was explained to him by Defne Aruoba [an interpeter].
In this statement he consented to his children undergoing medical and
other tests related to research on their quadrupedal gait, said he
understood that all information of relevance to their welfare would be
shared with him, and acknowledged that he had no objections to the
research being published. He signed a further statement for the BBC,
consenting to film and photographs of his film of his family being
broadcast."

In the paper itself, the authors present the geneology of the family,
showing how the trait appears to be hereditary. They refer to
unpublished research by Dr. Demirhan and German scientists, which has
since been published in the Journal of Medical Genetics here. The paper
identifies the gait as a genetically linked trait, which they traced to
chromosome 17p.

The British authors also make observations on how the members of the
family walk, how they can still do various things with their hands, and
so on. They publish an MRI scan of one family member, showing that the
brain is deformed, particularly in the cerebellum, which controls
movement. They point out that the family walks in a gait seen in a
small percentage of babies, called a bear crawl. It's possible that
they simply never moved beyond the bear crawl, perhaps because they had
difficulty balancing on two legs.

The end of the paper speculates on the evolutionary implications of
this family. The authors raise an old hypothesis that our quadrupedal
ancestors went through a stage in which they walked on their wrists--as
the Turkish family does--before becoming fully upright. "Does it in
fact represent and atavistic trait, that has been exposed--possibly for
the first time in recent human history--by the remarkable conjunction
of circumstances?" they write. Later, they add, "We think it is
arguable that, in these modern human quadrupeds, we are indeed seeing
the 'rediscovery' of something very like the quadrupedal gait used by
our ancestors."

So, where does that leave us? The independent research on the family,
and the findings of a genetic link, are consistent with the idea that
this is not a hoax. I'm still skeptical about the claims about our
ancestral gait. If a child is born blind, you can't automatically say
it has leapt back to our eyeless ancestors.

As for the dispute, some questions still linger. Dr. Humphrey claims I
am spreading "empty gossip." But these accusations did not come from a
some random guy on the street in Istanbul. They came from one of the
scientists that Dr. Humphrey himself says invited him to look at the
family in the first place. Dr. Tan himself published his own research
on the family in the March 2006 issue of the International Journal of
Neurology. So this is not empty gossip. It is a serious charge from
another scientist who collaborated with Dr. Humphrey and who has
published research in a peer-reviewed journal (which Dr. Humphrey has
yet to do). The charges may well be false. Dr. Humphreyshimself has not
offered his own account of this falling out--either in his paper, in
this blog, or in the original news article. What happened?

Here's another question: if Dr. Humphrey and his colleagues did not pay
the family, as he maintains, then what about the television production
company that made the documentary? The producer contacted for the
article I mentioned refused to comment on the controversy. It appears
that the researchers and the TV producers worked quite closely
together. The authors thank one of them in their paper for filming.
It's one thing for a TV producer to pay someone to be on their show.
But if scientists are standing right next to those producers as they
hand out cash, hoping to do scientific research, it can certainly take
on the cast of an indirect pay off.

Let's be clear, however: this is only a question.

I think it's important question, however, because it deals with an
ethical swamp that more and more scientists have to wade through.
Scientists sometimes collaborate and receive grants from media-related
companies. It's expensive to go off to some distant land and do
research, and scientists have to be creative about finding money. But
if you depend on a company for your funding, you may have to think
about how your dependency influences your science. For example,
scientists may be prodded to go public with information that has not
yet passed peer review. See, for example, the Archaeoraptor case. I
wrote about a similar episode of ethical cheesiness in a 2004 review of
the book, The God Gene, for Scientific American. I pointed out how the
author, a geneticist, was happy to go ahead with writing a book for the
public even before his results had been accepted in a scientific
journal. The book turned out to be a smash, and the author had no
problem going on lots of television shows to talk up his work and sell
more copies. But guess what? It's 2006, and he still hasn't published
anything in a journal.

Finally, there is the issue of the show itself. I'll have to get my
hands on the show to judge for myself. That may be tricky, since I
don't have cable (for reasons of self-preservation; I'd watch it all
day). It would seem to me that the biggest challenge to making a
"responsible" show, as Dr. Humphrey calls it, would be to overcome the
voyeurism that seems to be built into a situation in which a film crew
flies from Britain and observes a family of poor outcasts who collect
cans and bottles to make ends meet. We shall see.

All comments are welcome--from Dr. Humphrey, from ethicists, from all
readers.

Update 3/10/06: Dr. Humphrey, cut off from the blogosphere, asked me to
pass on this response to my latest remarks:


At Tan's urging - I gave the Turkish family 500 euros (about
$400) to compensate them for the trouble caused by our intrusion, but
with no other strings attached. The TV company later also helped them
out in a limited way - and not to have done so, would have been
exploitative.

.

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