Thursday, February 26, 2009

How Strong is a Chimpanzee?

John Hawks has a very interesting article in Slate in which he looks at the experiments that have been done to find out how strong chimpanzees really are.
As it turns out, claims of chimpanzees being 5 to 9 times stronger are exaggerated, but they are still about twice as strong as humans.
The short article makes for really enjoyable reading, Go check it out.

I was surprised to read that that a chimp on all fours can easily outrun a human sprinter...

Monday, February 23, 2009

Michael Tomasello - The Origins of Human Communication (summary pt. 3)

I wanted to finish this summary on the weekend but just didn't get round to it because I've got a lot to do right now. Here it is anyway:

Like I said in my last post, the rest of Chapter 2 focuses on what in the chimpanzee/human lineage provided a basis for modern language.


One crucial factor is chimpanzees' ability to use and comprehend pointing.

In the wild, chimpanzee pointing is very rare. But approximately 60 to 70 percent of all captive chimps spontaneously use pointing in an imperative manner in their interactions with humans, e.g. by pointing to food that is out of reach as a request for the human to get it. But pointing gestures that aren't imperative are virtually absent. This even applies to language-trained apes such as Kanzi. In the few studies that have been done on this, 96-98 percent of all their pointing were imperative. The other 2-4 had no clear function.

Thus there is nothing in chimpanzees' pointing behavior that would suggest that they are capable of or interested in sharing attention within a joint attentional frame.

On the other hand, in a Brain Science Podcast interview, Stuart Shankar, co-author of The First Idea: How Symbols, Language, and Intelligence Evolved From Our Primate Ancestors to Modern Humans , reports of a an encounter he had with the bonobo Panbanisha in which she showed him various plants and classified them, for example, as poisonous. Shankar interprets this as truly sharing attention and informing for the the sake of informing, but Tomasello argues that these kinds of gestures are not to be seen as as truly declarative or informative, as they are more

recognitory or classificatory, as the ape simply recognizes something and produces the associated sign in recognition“ (Tomasello 2008: 38).

Comprehending Pointing

Interestingly, chimpanzees are much worse comprehending other people's pointing than they are producing it themselves.

In a cool experiment, Tomasello and his colleagues have shown that in a cooperative situation, chimpanzees are unable to grasp the fact that the hidden food is in the bucket that the experimenter is pointing to. Human infants, on the other hand, are able to understand this task by 14 months of age. (Behne et al. 2005) In a competitive version of this task, however, chimpanzees fare much better (Hare & Tomasello 2005). These results suggest that chimpanzees have problems with "shared intentionality," i.e. recognizing situations where you have shared cooperative goals with others and have the same shared attentional frame.

Intentionality & Perception

According to Tomasello, apes and young human children both attribute simple forms of intentionality to other actors. For example, when a human repeatedly tries to give food to a chimpanzee but fails because he is clumsy, the chimp reacts patiently, whereas he gets frustrated when the human is failing to pass him the food for no good reason or because of unwillingness.

Most of the time enculturated chimpanzees also imitate

demonstrator’s action more often when he freely chose his action than when he was forced to use it by some constraint” (Buttelman et al. 2007: F37, see here).

Crucially, chimpanzees also understand that others have perceptions and see things. In a competitive task with a dominant chimpanzee, for example, subordinate chimps, secretly take a food reward when the other one is unable to see him, but not when the food can be seen by the dominant chimp.

According to Tomasello then,

"The overall conclusion is thus that apes understand others in terms of their goals and perceptions and how these work to determine behavioral decisions, that is, they understand others as intentional, perhaps even rational, agents (Tomasello 2008: 4)
Intentionality + gestural fexibility = evolutionary foundations of language ?

This seems to be the conclusion Tomasello draws at the end of the second chapter. Clearly, when a chimpanzee produces a gesture, he does this in a very flexible manner that even shows sensitivity to the attention of the other. Ape vocalizations on the other hand are mostly inflexible and do not take into account the presence or absence of attention to the displays. Thus there is strong evidence that the capacities apes display in the gestural modality

"are the original font from wich the richness and complexities of human communication and language have flowed. " (Tomasello 2008: 55).


Behne, T., Carpenter, M., and Tomasello, M. (2005). One-year-olds comprehend the communicative intentions behind gestures in a hiding game. Developmental Science, 8, 492–499.

Buttelmann, D., Carpenter, M., Call, J., and Tomasello, M. (2007). Enculturated apes imitate rationally. Developmental Science, 10, F31– 38.

Hare, B., and Tomasello, M. (2004). Chimpanzees are more skillful in competitive than in co-operative cognitive tasks. Animal Behaviour, 68, 571–581.

Tomasello, Michael (2008): The Origins of Human Communication. Cambridge, MA; London, England: MIT Press.

Monday, February 16, 2009

Charles Darwin & W. Tecumseh Fitch & Derek Bickerton on the Evolution of Language

Over at Language Log there are two very nice guest posts on the occasion of Darwin's 200th Birthday and his view of the evolution of language. The first post, by W. Tecumseh Fitch of St. Andrew's University, in which he reexamines Charles Darwin's proposal that the ancestors of humans first developed a emotionally expressive musical protolanguage which later developed into modern meaningful symbolic language. He discusses this view in the light of present-day evidence and concludes that
"suitably updated, [it] provides a compelling fit to both the phenomenology of modern music and language, and to a wealth of comparative data. "
He further argues that:
"This year of Charles Darwin's 200th birthday seems an opportune time for Darwin' own model of language evolution to regain the prominence it deserves."
In the second post, Derek Bickerton comments on Fitch's essay and critices his verdict that

"Darwin's view of language was ahead of its time, and his model and arguments remain surprisingly relevant."
Instead, he argues, although Darwin got a lot of things right,

"in many cases he was, inevitably, limited by the state of knowledge in his time."
In regards to the speculations on the evolution of language, Darwin's lack of knowledge about the ancestral environments of pre-humans ist the graves limitation.

In a savanna environment in which much of homo evolution supposedly took place, a musical, singing way of communication would simply be bizarre and even extremely dangerous because it would attract predators.

This is a problem Bickerton sees with a lot of theories of language evoltion. For example, he also critized the lack of regard for the environmental context of language evolution in a review of James Hurford's fantastic book, "The Origins of Meaning:"
"Hurford gives a favorable mention to niche construction theory, and I kept hoping he was going to draw the conclusion I drew from it: that the key to the origin of language must be sought somewhere among the niches constructed by human ancestors between the date of the last common ancestor of humans and other apes and the present—niches very different from any occupied by other apes. But he did not."
For Bickerton, Darwin, unknowingly, and Fitch, unwittingly, have made the same mistake:

"The notion of a terrestrial and heavily-predated primate indulging in any form of vocal activity-especially one that must, in quantity as well as quality, have exceeded those of all other primates barring gibbons-is simply bizarre,."

Both posts make for very interesting reading and I'm looking forward to the publication of both Bickerton's "Adam's Tongue" (out next month) and Fitch's book "The Evolution of Language" which apparently is in press as well.

Update: W. Tecumseh Fitch has replied to Bickerton's criticism with a post with the entertaining title ""Silence on the Savannah!" On Bickerton's Yodeling Australopithecines and Missing the Point of Musical Protolanguage"

Thursday, February 12, 2009

Happy Birthday Charles Darwin!

So today is Darwin's 200th Birthday, aka Darwin Day.
There are quite a lot of interesting posts up.
John Wilkins adresses the myth that Darwin didn't actually adress the origin of species in his book, and Ed Yong has tackled human evolution in the 6th post of his 8 part series celebrating Darwin's bicentennial.

There's also a lot of discussion on how to assess Darwin's importance in modern evolutionary biology, especially about the usage of the term "Darwinism" (for positive voices see for example, here, here, for more negative assesments see here, here, and here)

Overall, I like the assesment made by John Wilkins in his very nice article "Not Saint Darwin:"

"What we remember Darwin for is a synthesis and the empirical support he brought in its defense. He brought together many ideas that were `in the air', so to speak, reading more widely than almost anyone else as well as doing his experimental and anatomical work, and more importantly, managed to filter out most of the bad ideas.

Darwin's achievement was to identify crucial questions and offer a coherent theoretical account that answered them

So let us remember Darwin not as the discoverer of anything (apart from the cru-
stacean nature of barnacles etc.), but as the guy who set of a fruitful, active, com- plex and ultimately explanatory research program in biology, which continues to become ever more active.
Don't make him a saint, an authority, or a hero. He's just a damned good scientist."

Wednesday, February 11, 2009

Preparing for Darwin's Birthday: Celebrations & Myths

Tomorrow is Darwin's 200th Birthday and all over the blogosphere and in magazines, TV etc. there are a lot of interesting things on Darwin, "Darwinism", and evolutionary biology.

Some Highlights:

Ed Yong of Not Exaxtly Rocket Sciene has started a 8-posts series on evolutionary research to celebrate Darwin's bicentennial. The topics covered so fare are

Posts on evolutionary arms races, human evolution, virus evolution, and co-evolution and horizontal gene transfer are still to follow.

John Wilkins of Evolving Thoughts will try to clarify some of the oft-repeated myths about Darwin and his ideas.
These will include:

  • Darwin did not believe in the reality of species
  • Darwin did not explain the origin of species in The Origin of Species
  • Darwin was actually a Lamarckian
  • Darwin was a gradualist
  • Darwin thought evolution relied on accidents and chance
  • Darwin thought everything was due to natural selection
  • Darwin thought that Australian aborigines were closer to apes than to Europeans
  • Darwin was a social Darwinian
There are some things in there I thought to be true. But otheres are pretty obvious. Just for fun I'll quicky adress two of these myths (although John Wilkins will have a lot mor to say about them, of course), and add another one that's not a myth but just a wrong assumption.

Myth: Darwin thought everything was due to natural selection
Wrong. In The Origin of Species he clarifies that:

"I am convinced that Natural Selection has been the main but not exclusive means of modification. (69)"

In this book he also introduced the factor of sexual selection, i.e. the fact that evolutionary change can also be influenced by females choosing mates with certain traits.
In his 1871 book adressing human evolution, The Descent of Man, Darwin tried to explain the evolution of many of the mental powers of humans in terms of sexual selection.

It is also important to note that in this book Darwin also pointed out that:
"Important as the struggle for existence has been and still is yet as far as the highest part of our nature is concerned there are other agencies more important"
This also brings us to the next Myth

Myth: Darwin was a Social Darwinist
No. People who advocated these ideas of laissez faire capitalism were Herbert Spencer, John Fiske and William Graham Sumner (although it is debated how much he really was a Social Darwinist). They came up with this ideads after reading Darwin, but more often, (as in the case of John Fiske), after reading Herbert Spencer interpreting Darwin in his own way.

Also, Darwin is sometimes quoted a promoting eugenics with this statement:
"It is surprising how soon a want of care, or care wrongly directed, leads to the degeneration of a domestic race; but excepting in the case of man himself, hardly any one is so ignorant as to allow his worst animals to breed."
But as we have seen above, for humans there are other agencies more important and this is why he continues:
"If we were to intentionally neglect the weak and the helpless, it could only be for a contingent benefit, with overwhelming present evil. Hence we must bear without complaining the undoubtedly bad effects of the weak surviving and propagating their kind"

Another popular misconception, not really a myth, is that Darwin coined the term "survival of the fittest." But in fact the term was coined by Herbert Spencer (who had already proposed his own concept of evolution in 1855) after reading Darwin. Darwin then used the term in later versions.

The New Scientist also has a page up on 24 popular misconceptions about evolutionary theory

There's also another reason to celebrate: Carl Zimmer of the Loom has announced that he's writing a textbook for non-biology-majors and the general reader called The Tangled Bank: An Introduction to Evolution and it's going to come out this year in August. Woohoo!

Wednesday, February 4, 2009

Thomas Henry Huxley: Why Evolution Matters

This semester I'm attending two very interesting seminars: one one the Reception of Darwinism in America in the 19th and 20th Century and one one its philosophical and theological implications from todays perspective.

In my reading pack I just found a very nice quote by "Darwin's Bulldog", Thomas Henry Huxley (1825-1895):

"The question of questions for mankind --the problem which underlies all others, and is more deeply interesting than any other--is the ascertainment of the place which Man occupies in nature and of his relations to the universe of things. Whence our race has come; what are the limits of our power over nature, and of nature's power over us; to what goal we are tending; are the problems which present themselves anew and with undiminished interest to every man born into the world."
(T.H. Huxley, Evidence as to Man's Place in Nature, 1864, p. 58)