The Bushmen are not primitive! (not necessarily)

By Razib Khan | September 30, 2010 2:38 am

324_1035_F1To the left is a figure from the 2009 paper The Genetic Structure and History of Africans and African Americans. This paper happens to have excellent coverage of African populations, and the figure is a phylogenetic tree generated from distances between those populations, as well as some non-African ones. I’ve labelled the broad clusters. The Bushmen* branch off first, along with the Pygmies. The other clade represents all other humans, African and non-African. Following the non-Bushmen/Pygmy clade down its branching pattern all non-Africans eventually go their own way, and differentiate into their various groups. South Asians form a clade with Europeans and Middle Easterners. East Asians, Native Americans, and more broadly Oceanians, form their own clade. Outside of Africa you basically have a west vs. east & further east division.

These trees are essential in helping us visualize genetic relationships. Tables of pairwise distances are simply not as informative as representations of the data for the human mind. More colloquially, they blow. Trees and two-dimensional plots are much better representations of the data which we can digest in a more gestalt fashion. We see, therefore we know. Ah, but even the innocent tree can lead a mind astray. Or at least this particular tree. So let’s try something different.


abofig1Here’s a figure from Whole-Genome Genetic Diversity in a Sample of Australians with Deep Aboriginal Ancestry. This tree has a smaller number of populations, but the broad geographical relationships are the same. West Eurasians are one cluster, while East Eurasians, Native Americans and Oceanians are their own super-cluster which divides further. Among the Africans you see that the Bushmen and the Mbuti again exhibit more distance from the other groups. But the biggest difference is that the tree is unrooted, so you don’t immediately orient yourself from outgroup to ingroup in a serial manner.

Now let’s look at a headline inspired by one of the papers: African San people – the world’s most ancient race. Going by the figures which paper do you think it was? It was the first paper of course. There’s a huge problem when these phylogenetic trees are generated that human outgroups, or basal clades, are defined as ‘ancient,’ the ‘oldest,’ or the most ‘antique.’ This is just confusing. Not only that, as a person deeply committed to the dignity of the indigenous peoples I am offended! I generally get irritated or blow a gasket when people make that confusion in the comments, because I think it leads to lazy inferences. One of my main quibbles with The Faith Instinct is that Nicholas Wade used the Bushmen as proxies for ur-humans to reconstruct prehistoric religious practice, implicitly relying on the fact that they’re the basal lineage in most genetic studies as if they’re a fossil which we can use to paint the past.

phytreeIn any case, I was going to recommend to readers that they just refer to ‘basal clades.’ Well, I’m not a taxonomist obviously so I decided to look in the literature, and I found this paper, Which side of the tree is more basal? The tree they use to illustrate the lack of utility of terms like ‘basal clade’ is to the left. Let me quote them:

Both branches originating from a node (i.e. the two sister groups) are of equal age and have undergone equivalent evolutionary change. Whether a group has branched off early (basal) or later in the phylogeny contains no information about this particular group, but information about both this group and its sister group, because both branched off at the same time. By notation we tend to portray one branch (the species/taxa-poor one) as being on the left, and the other (species/taxa-rich) as right – but this infers nothing about their evolutionary development, only about their taxon richness (speciation less extinction) at a given geological period (mostly the present), or, even worse, about the taxon sampling pattern in the particular study. Different taxon sampling leads to different interpretation about ‘the most basal clade’….

Considering clades or taxa as ‘basal’ is not only sloppy wording, but shows misunderstanding of the tree and may have severe semantic and argumentative implications. Declaring one sister group to be basal gives the other sister group a higher or at least a different value (‘the basal clade’ vs. ‘the derived clade(s)’). If the Polyneoptera is the most basal clade of the Neoptera, then the rest of the Neoptera (the Eumetabola) is given a higher value (as the ‘main’ body of the group). Admittedly, it contains more species, but this is not a quality necessarily granting it higher value…..

If the phylogenetic tree in Fig. 1 is correct, Polyneoptera and Eumetabola are sister groups. There is no necessity to term either as ‘basal’. Even if one wants to avoid the little-used name Eumetabola, it is easy to describe the Polyneoptera as the sister group of the remaining Neoptera. Argumentation with sister-group relationships is easy and shows relationships much more clearly than declaring one sister group to be basal. The ‘basal position’ within an ingroup always means ‘sister to the remaining taxa’, so say so!

The argument here is obviously embedded in the milieu of systematics and their particular concerns. But their objection to the term ‘basal clade’ is actually pretty much my main qualm which using terms like ‘ancient.’ I don’t think using ‘sister to the remaining taxa’ is going to be informative to most people, so at this point I don’t know what I’ll use for short hand. Outgroup seems viable.

I don’t really think about systematics in a deep philosophical sense. But the problem of terminology here, and the evolutionary implications therein, have brought home to me utility of a precise and accurate systematic framework in biology.

* The term “San” is like the term “Lapp” or “Welsh,” what others call them, so I’ll use Bushmen.

CATEGORIZED UNDER: Evolution
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  • Georg

    Who is primitive?
    What
    criterion is used to define whether some people has
    advanced to Bronze or Iron age?
    Using (traded) iron or when they they produce iron
    themselves?
    The latter criterion would say that Finns are in Iron Age
    not more than 100 or 300 Years maybe, and the Sami have not
    arrived in iron age yet.
    I think the Eskimo people deserve admiration for mastering one
    of the worst climates in the world, without metals and only
    very limited wood supply.
    I think of Bushpeople in a similar way.
    Georg
    BTW This name was given by Boers or Germans first,
    (Buschmänner, Buschfrauen, Buschleute in German,
    Nederlands is similar I suppose) maybe You like “Bushpeople”?

  • onur

    I think the term “basal” should only be used for the ancestral (really ancestral) state of a genotypic or phenotypic variant as opposed to the derived state. “Outgroup” is the correct term for the Bushmen and Pygmies.

  • Mary

    I thought about the question of ‘who is primitive?’ when reading about the Dani people of the west central highlands of New Guinea. Since being discovered by the west in the last 50 or so years, they’ve allowed themselves to be objects of tourist curiosity, but otherwise have kept their neolithic ways . I can’t find any recent information about genetic studies of them if there are any. They use tobacco, and sweet potatoes are their main food crop. These are not plants native to New Guinea in the information I can find. They may have had previous contact with westerners.

    My point, I suppose, is can we put the tribal leader and Bill Gates next to each other and call them both 21st century men? I suppose we must.

  • http://raysawhill.com Ray Sawhill

    So what do you think of anthropologists using present-day hunter-gatherer types as proxies for “original humans”? Valid? Not-valid? Maybe useful in some ways? An insult to indigenous people everywhere?

  • Katharine

    I think it’s awesome that there’s greater human genetic diversity within Africa than outside it.

    I think it makes it even more imperative that public health efforts within Africa be stepped up, because we focus a lot on biodiversity within species other than our own – we also need to look at genetic diversity within our own species. Someday we may need it to stay alive.

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    So what do you think of anthropologists using present-day hunter-gatherer types as proxies for “original humans”? Valid? Not-valid? Maybe useful in some ways? An insult to indigenous people everywhere?

    i think it needs to be done carefully. many of these HG’s are not representative of pre-modern HG’s cuz they’re HG’s for a reason (e.g., marginality of the land).

  • onur

    Someday we may need it to stay alive.

    What do you mean by that?

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    i assume she means disease resistance. the main objection i’d have to that is that disease related loci are generally high polymorphic….

  • omar

    It may be hard to argue that a successful species with 6 billion individuals is in critical “need” of any particular genetic information that may be unique to one small group. Of course, there may be unique Bushman sequences that may turn out to be useful for something, but I wouldnt pin the need for their survival on this particular argument. Can’t we just say that everyone deserves a chance to live? we shoudlnt approve of a “Bushman genocide” even if it turns out that they have not a single unique gene….

  • Yawnie

    If Black Africans have been around a long time then the contenders for earliest known ‘Black African’ type skeleton should not be more recent than the eariest Khoisan type remains.

  • Ian

    I agree that it’s ridiculous to speak of “ancient” groups (of any taxon, even so-called “living fossils”), and speaking about “basal” with an unrooted tree only showcases one’s own prejudices. (After all, we expect “primitive” people to look and act a certain way.) And while I realise that it would be politically difficult to actually add an outgroup to a human phylogeny, I’d be very curious to see what it would look like. Though, of course, I’m guessing it would depend on the genes you select…

  • http://occludedsun.wordpress.com Caledonian

    even if it turns out that they have not a single unique gene….
    There’s a lot we might be able to learn from their genetics, even if all of their individual genes are found elsewhere. It’s the combinations that are important – and if some combination is found in their genome at a much higher frequency than others – or absent in the same way – that could lead to very exciting insights.

    One question: is it generally insulting to people from an ethnic group for others to discuss its preservation?

  • gcochran

    Logically, there is a sense in which Bushmen _are_ closer to the root of the tree and have _not_ undergone equivalent evolutionary change to some of the other branches.

  • onur

    Logically, there is a sense in which Bushmen _are_ closer to the root of the tree and have _not_ undergone equivalent evolutionary change to some of the other branches.

    In that relative sense Bushmen can be called primitive (not because they are frozen in time, but because they have undergoned less evolutionary change than most, if not all, other human branches/groups).

  • Mary

    But the same amount of time has passed for Bushmen to evolve as other branches. Doesn’t time determine how far from the root humans have evolved and so all present day branches are equal distant from the root?

  • onur

    Doesn’t time determine how far from the root humans have evolved and so all present day branches are equal distant from the root?

    Not just time, but also culture and nature (including climate). Agriculture and civilization have triggered many important evolutionary changes in humans in the last 10.000 years. Quite naturally, hunter-gatherer societies have minimally undergone, if any, these kinds of evolutionary changes.

  • onur

    Typo correction for “undergoned” in #15: undergone

  • gcochran

    Or you could say that the branches that left Africa underwent more adaptive evolution because they were exposed to new environments – but what I was really thinking about was Neanderthal admixture, which apparently only happened to some of the branches. You see, the tree isn’t a tree.

  • onur

    Or you could say that the branches that left Africa underwent more adaptive evolution because they were exposed to new environments – but what I was really thinking about was Neanderthal admixture, which apparently only happened to some of the branches. You see, the tree isn’t a tree.

    I didn’t mention them, because I was focusing on the agriculturist/hunter-gatherer dichotomy rather than the African/non-African one. But I think the African/non-African (including North Africans in the non-African category) is another important dichotomy in humans in terms of evolutionary change.

  • http://abugblog.blogspot.com Blackbird

    Thank you for pointing this issue out. I think ‘basal’ can be correctly applied to the first node or split in the tree, not to the branches themselves. The split between the san, on one hand and the rest of humans, on the other – for mtDNA and Y chromosome – would be the basal split in a phylogenetic reconstruction. But I agree, ‘basal’ is misused all the time!

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This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!

About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com

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