Tag Archives: Human Evolution

Palaeowomaen: Barbara Isaac, Women in The Field, and The Throwing Hypothesis

Following on discussion arising from this post, here is a revised discussion of throwing in human evolution.

The question of diversity in science, and more specifically, success for women, is often discussed in relation to bench or lab oriented fields. If you read the blogs that cover this sort of topic, they are very often written by bench scientists, for bench scientists, and about bench scientists. Which makes sense because most scientists probably are bench scientists.

Here I want to do two separate but related things. I want to discuss certain aspects of the nature of fieldwork in my area in the 20th century that have had a strong effect on the way women have pursued their careers (or not). Although I characterize this as the situation of the 20th century, this does not mean that the situation has or has not changed substantially since then. Simply put, I’m not discussing the current career related situaton for women in field paleoanthropology here in this post.

The second thing I want to do is to talk about a successful female social scientist with a strong connection to fieldwork in palaeoanthropology, as well as theoretical and administrative contributions. This person is also someone who straddles the boundary between classic mid- to late-Twentieth Century patterns of professional activity (in these field sciences) and more recent patterns. I’m speaking here of Barbara Isaac.

The link between these two topics is a bit tenuous but it is also meaningful. There is nothing stereotypical about Barbara Isaac’s career, and there is nothing short of admirable about her as a person and a scholar. My intention here is to not make strong links between these two parallel topics.
Continue reading Palaeowomaen: Barbara Isaac, Women in The Field, and The Throwing Hypothesis

A Book about Taung and "the Hobbit"

The Fossil Chronicles: How Two Controversial Discoveries Changed Our View of Human Evolution is by a scientist Dean Falk, who has contributed significantly to the study of evolution of the human brain, and who has been directly involved in some of the more interesting controversies in human evolution.

Back when I was a graduate student I was assigned by my advisor a set of literature to absorb and comment on. The mix of published and soon to be published papers included a series of papers written by Ralph Holloway and Dean Falk. These represented a fight over the interpretation of early hominid brains as studied through endocasts. Endocasts are fossilized casts of the inside of an animal’s brain case or the artificially produced version made of casting material poured into a skull. Either way, you get a roundish blob that resembles the exterior of the original brain. Endocasts are of limited value, as layers of tissue in a living mammal separate the brain from the skull, attenuating detail. As Falk point out in her book, endocasts are a rather “surficial” view of a brain, but are not without their uses.

Fossil endocasts are compared to endocasts made from the skulls of “living” primates and humans, which in turn are understood via Continue reading A Book about Taung and "the Hobbit"

Evolution for Conservative Christians

Lewis Black has a formula for addressing creationists. You carry around a fossil. Then, when someone starts talking about creationism, you pull it out and hold it up in plain view and say “Fossil!” Then, if they keep arguing, you throw it over their head. That makes me laugh.

Despite the fact that I am a raging secularist and activist atheist, not all of my friends are. And, I have a friend for whom I have nothing but love and respect who happens to be a fundamentalist evangelical Christian. Personally, I’m sure that down inside she is also an atheist, and I know she knows I think that of her, and it is sometimes a matter of discussion. Here’s the thing: She’s very very smart, knows a lot of stuff, and is on my personal top ten list of Most Thoughtful People. (Thoughtfulness is actually a characteristic of the regular non-Troll readers of this blog, so you know what I mean.) Anyway, she totally gets science even though she is not a scientist nor does she have a lot of training or education in science. (Rather, she can read numerous dead languages and has all sorts of other smarts.) She understand that science is real, it is a process of thinking and discovery, that it is important, and that it should shape much of our policy as a society. And all that is by way of introduction for the following video, which she has recommended. I’d like to know what you think of it:

So, if you don’t want to carry around a fossil, you can just carry around this video.

What is Dunbar's Number?

The term “Dunbar’s Number” refers to a particular hypothesis by primatologist Robin Dunbar. It is a very simple idea with rather complex implications, and it is one of those simple ideas that gets more complicated than ideal as we look into it more and more. Eventually, the idea is required by many who contemplate it to do more work than was ever intended, and in this way seems to fail, though it really doesn’t. I personally think Dunbar’s number is useful if it is properly understood, so I want you to give it a chance, and to help you do that I’d like to use an analogy.

I’m thinking of a number called Carrier’s Number. Carrier, in this case, refers to the company that installs air conditioners and heaters. Carrier’s number is the temperature in degrees F at which you, sitting there in your chair, notice it is too warm so you get up and go turn on the air conditioner. It is best measured as a post hoc number…we watch and wait, flies on the wall, as the room heats up, and when a person gets up and flips on the air conditioner, the temperature at that point was carrier’s number for that person at that time.

One might argue that a post hoc measure like this isn’t much use in science because in science we like to predict things. But just because carrier’s number is best measured pot hoc does not mean that it only exists post hoc. It existed before the test subject got up, we just didn’t know what it was. For a large number of test subjects, we should be able to estimate carrier’s number (it is probably in the upper 70’s F). However, this will vary across cultures, across seasons, humidity, as clothing styles change (in the days of Polyester Leisure Suits, it is said that Carrier’s Number went down by about four degrees) and so on. The fact that it varies does not make it a bad number. In fact, its variation and reasons for it can make it an extra good number depending on what one is trying to do with it.

Dunbar’s number is the number of full blown social interactions you can manage. This number is lower or higher across species of social primates, as it tracks adaptive suites of sociality and the ability of brains to manage sociality. So, you can measure Dunbar’s number across primate groups by looking at how large effective primate groups get across species and figuring that the number is just about that maximum group size. Or, you could estimate Dunbar’s number (retrodict it, as it were) by looking at relative brain size, if we assume that brain size is linked to Dunbar’s number, all else being equal. In this way, Dunbar’s number is a way of linking primate sociality with brain evolution, which was the original idea.

In modern society, and in human historical contexts, we may see Dunbar’s number in a lot of places. This is the number at which, more or less, groups start to break down (in some societies) and villages split. Military units max out at about Dunbar’s number (companies are about 100 in size) and so on. This does not mean that Dunbar’s number and its associated dynamics explain everything. It might mean that the breakdown of social interactions can be more important than, say, resource limitations, on human group fission and fusion. That is exactly what many anthropologists have been suggesting for decades. Dunbar’s Number is simply this concept quantified somewhat and expanded to primates.

There are variations and adjustments. Some organisms have apparent smaller brain size because their diets cause a different body size, so that has to be adjusted for (leaf-eating monkeys may small relative brain size because their bodies are large, not because their brain is small, for example). What a fully blown social interaction is may vary. A group of primates may have a subgroup that hardly ever interacts with the others. Perhaps pre-adolescent monkeys don’t count for as much as sexually mature monkeys, so if there happens to be a baby boom a couple of years back, the group size if you count everyone is higher than Dunbar’s number. Or perhaps the group includes two or three social geniuses who temporarily facilitate an extra large group size, or temporarily force an extra small group size, for some reason.

It makes sense that there is a limit on effective sociality, and thus, on effective social group size. Dunbar’s number is nothing other than the number you end up with because when you are making the damn graph you need a damn number to put there on one of the axes. It has been over-interpreted or over-used as a number like many of those from Physics, like the freezing point or boiling point of water, which it is not.

Desiree Schell and I spoke about Dunbar’s Number on the Skeptically Speaking that just became ready for you to download. Check it out here.

This video includes, during the last third somewhere, a discussion by Dunbar of all this.

And, here’s a few items by Dunbar you might find interesting:

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  • How Many Friends Does One Person Need?: Dunbar’s Number and Other Evolutionary Quirks
  • Grooming, Gossip, and the Evolution of Language
  • Philip Tobias 1925-2012

    Philip Tobias passed away this morning, according to a mutual friend. I’ve not heard any details.

    Tobias is the most important hominid anatomist to have lived in the 20th and early 21st century, having taken the chair originally established by Raymond Dart at Wits University. He literally defined several of the hominids, being the anatomist to author the official diagnosis of several species. He was also a human rights champion, an excellent poet and decent singer and performer, an excellent teacher, a great friend, a strong and central personality in human evolution and unbelievably demure and humble for a man of such stature.

    Philip Tobias

    I remember the first time I met him. I was standing in the lobby of the Peabody Musuem, where we were hosting an LSB Leakey Foundation Event. I had just seen off Gordon Getty and his staff who were heading for lunch, ridden down the elevator with Yo-Yo Ma, I’m pretty sure the Presidents of two or three countries were milling around and some other stuff was going on when Mary Leakey and Philip Tobias walked up to me. I instantly dropped all the other names and gave them my full attention.

    “We heard you might be able to drive us to the bookstore,” one of them said. “Harvard Square is meant to have some good ones.”

    I thought for a moment and it occurred to me that I might not be a normal graduate student because I hadn’t soiled myself yet. Truth is, I wasn’t, having had a normal live before I started the project of Piling it Higher and Deeper.

    “I can,” I replied. “My pickup is out in front, but it has a miniature cab. One of you will have to ride bitch.”

    They walked to the bookstore.

    The last time I met Philip was in his lab at Wits. I’ve told part of that story before, so I won’t bother you with it now.

    RIP Philip. Thank you for everything.

    Two New Books on Human Evolution

    The Fossil Chronicles: How Two Controversial Discoveries Changed Our View of Human Evolution and Born in Africa: The Quest for the Origins of Human Life are two very recent books on human evolution, both of which I recommend, depending on your interests.

    The first is by Dean Falk, who has studied brain endocasts for the last 30 years. Falk chronicles her early work on endocasts, the relationship between that work and the much earlier work of Raymond Dart, in South Africa on the first Australopith fossil, and touches on the problems of being a woman with somewhat controversial findings to report, in a largely patriarchal field of study. But all that is just background for Falk’s description of her work on the famous Hobbit remains from Flores, Indonesia; She was called in to study the brain endocasts of one of those very famous fossils.

    Meridith’s book is an overview of the life and times of the “fossil hunters” working in Africa over several decades, from the times of, once again, Raymond Dart, to more recent times. I had thought I had heard all the dirt on these researchers, but Meridith has a few interesting items that were new to me.

    These two books are very different from each other in what they intend to do and the material they cover, but there are numerous overlaps and relationships between the two. I’ve written a review of the two books, together, for print publication, and when that comes out in several weeks I’ll point you to it, and I won’t say more here about them here. I liked both books, and I wanted to get this notice out now because the pair would make a nice holiday gift for the person in your live who likes this stuff … they are fairly recent publications.

    “Monkeys on our backs” by Richard Tokumei will not even make good toilet paper

    Richard Tokumei has written a book that is so bad he is ashamed to put his own name on it. “Richard Tokumei” is the pen name of a ‘writer/editor in Southern California [with] degrees in Humanities and Phychology from the University of California Berkeley” and he has produced a book designed to anger everyone who hears of it in order to create needless sensation and thus, sell copies. Which, once people get their hands on, will make rather low quality toilet paper.
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    What is the most important human adaptation?

    Human infants require more care than they should, if we form our expectations based on closely related species (apes, and more generally, Old World simian primates). It has been said that humans are born three months early. This is not accurate. It was thought that our body size predicted a 12 month gestation, and some suggested that Neanderthals would have had such, but this research conclusion has been set aside based on new analysis. But it is still true that developmentally, human children do not reach a stage of development that allows some degree of self care for a very long time compared to apes. The actual sequence of development is not directly comparable: It is not the case that after a certain amount of time humans reach a specific stage reached earlier in the lifecycle by Chimpanzees, as the differences are more complicated than that. For the present purposes, we can characterize the human condition for early development like this: Human babies are more helpless in more ways and for longer than comparable ape babies.
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    Falsehood: Humans evolved from apes

    Is it a Falsehood that Humans Evolve from Apes?

    How about this one: Is it a Falsehood that Humans did NOT evolve from Apes????

    Yes and no. Humans descend from a population of primates from which other apes also descended (minimally the two species of living chimps) and which was part of the panoply of late Miocene forms, all related to each other, that we call apes. So yes, humans evolved from apes.
    Continue reading Falsehood: Humans evolved from apes