Nick Matzke posted Entry 2614 on September 30, 2006 04:05 PM.
Trackback URL: http://www.pandasthumb.org/cgi-bin/mt/mt-tb.fcgi/2608

Preview graphic of chart showing hominin cranial capacity over time. Different taxa shown by color/symbol. Summary: fossil hominid brain size over the last 3 million years. Data from De Miguel and Henneberg, 2001, chart by Nick Matzke of NCSE.  Free for nonprofit educational use.Due to popular demand I have made some more charts that are slightly more complex than the hominin cranial capacity chart from yesterday’s post.

In the first chart, I have taken the “favored” taxonomic labels for each specimen from De Miguel and Henneberg (2001). Many specimens have been put in different species or different genera by different taxonomists, but these are supposed to represent something like the consensus, as the authors judged it in 2000. Australopithecus fossils are in red with various symbols, early Homo fossils (Homo habilis and others just labeled “early Homo” or “Homo”) are in orange, H. erectus is in green, and the asundry variations on Homo sapiens are in blue.

Hominin cranial capacity over time. Different taxa shown by color-symbol. Data from De Miguel and Henneberg, 2001, chart by Nick Matzke of NCSE.  Free for nonprofit educational use

The vertical bars on the right side represent the variation in cranial capacity for modern human males and females, taken from the McHenry et al. 1994 chart.

We can see here a point made by an actual anthropologist in the comments to the other post, which is that cranial capacity is not constantly increasing in every species. By eyeball inspection, it looks like there was a surge between Australopithecus - Homo habilis - Homo erectus, then stasis for 500,000 years in erectus, then another surge over the last million years (but note that this has leveled off – modern humans actually have smaller brains than Neandertals). Of course (and I emphasize), eyeball inspection is not a statistical analysis, and even a statistical analysis of stasis and change in hominin species would require some decisions about which taxa are “good species”, and this turns out to be a rather difficult thing to decide for many specimens (see below). The models that De Miguel and Henneberg fit to the data indicate that if one take the broad view across all of the species for millions of years, swamping out local events and local stasis, there is a pretty consistent exponential growth trend.

One nice feature of this chart is that we can place creationist claims in a quantitative context and see if they are meaningful. As I mentioned last week, Casey Luskin of the Discovery Institute likes to manufacture a “gap” in the hominin fossil record by citing papers that prefer to label Homo habilis as Australopithecus habilis. That accomplished, he dusts his hands and declares that that is the spot that God intervened (er, “the designer”) to create the clearly human Homo erectus and its impressive 800 ml cranial capacity. Presumably this is also the spot where Luskin thinks the Intelligent Designer created proto-humans with 48 chromosomes which just happen to match the great ape chromosomes.*

Anyway, what actually happens to the evidence if we switch the labels on habilis? I’ve done just that in this chart:

Hominin cranial capacity over time. Different taxa shown by color/symbol. Homo habilis has been relabeled Australopithecus habilis. Data from De Miguel and Henneberg, 2001, chart by Nick Matzke of NCSE.  Free for nonprofit educational use

See, there’s no fossil evidence for human evolution now!

More fun with labels

It is often written that hominin taxonomy is contentious, with “lumpers” and “splitters” arguing about where to draw lines and what counts as a fossil “species.” I often wonder if this argument is useful activity, since really, the only people who actually think that fossil species should always be distinct and morphologically discontinuous from other species are the creationists. With evolution, species are not permanently stable entities, and here and there they are going to intergrade with other species. It’s just a fact of life that some species are going intergrade, and thus going to be impossible to describe completely with typological labeling. Some specimens will fall in group A, some in B, and some in-between.

Part of the paradox here is that taxonomy will be especially difficult where the evidence for gradual evolutionary change is especially good. I think you can see this somewhat in this next chart. Here, I have created a category called “multiple”, which applies to any specimen that received more than one species designation according to De Miguel and Henneberg 2001.

Chart showing hominin cranial capacity over time. Different taxa shown by color/symbol. Specimens where researchers have used more than one species name are listed as multiple and shown with open boxes. Summary: fossil hominid brain size over the last 3 million years. Data from De Miguel and Henneberg, 2001, chart by Nick Matzke of NCSE.  Free for nonprofit educational use

Of course, this isn’t perfect, since some of the species names causing some of the “multiples” are no longer in use and wouldn’t be considered “live” controversies in paleoanthropology. And there are some specimens given vague labels like “early Homo” that probably indicate taxonomic uncertainty, but this was the only designation available so I left them as-is. On the other hand, there does appear to be quite a bit of confusion about the boundary between Australopithecus and Homo, and about the differences between H. erectus and early H. sapiens.

The Excel spreadsheet is probably too big to upload on PT given our constant bandwidth issues, but I have emailed it to a number of people (my email is: matzkeATncseweb.org). It is not particularly “nice” looking at the moment, of course, but feel free to use/modify it for nonprofit educational purposes, with attribution. Someone with some bandwidth might even upload it on their website.

Notes

* Luskin postulates that the non-evolved 48-chromosome human ancestor then evolved into the 46-chromosome modern human through chromosome fusion, thus miraculously explaining away Kenneth Miller’s argument that the fused chromosome in humans is evidence of common ancestry with the apes. I Am Not Making This Up. Here is Luskin’s graphic:

I suppose he thinks the Intelligent Designer created the endogenous retroviruses and plagiarized errors we share with apes in the human genome also, just to be clever.

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Comment #136276

Posted by Philip Bruce Heywood on September 30, 2006 6:06 PM (e)

O.K., do some other species by way of comparison to find out what this data means in terms of speciation. E.g., Run all the permutations & combinations on cranial capacity in donkeys and horses and see whether we can’t “prove” that dankeys are evolving into horses. Incidentally, a bullock has a brain that we can make a meal from, but only desperate men make a meal from an entire crow - which comes in more intelligent than any bullock. Find what a species is, first; then you are entitled to hypothesize on the origin therof.

Comment #136288

Posted by Thought Provoker on September 30, 2006 6:14 PM (e)

Nick,

As always, you have provided very good and thought provoking information.

However, I will make the prediction that your A. habilis chart will be immediately quote-mined and offered as evidence that you, yourself, provided proof that Luskin was right after all.

Comment #136318

Posted by David B. Benson on September 30, 2006 7:13 PM (e)

Nick, this is a very useful exercise for me! As I read it, there is no evidence for H. erectus more recent than about 75,000 years ago, but there is more recent evidence of Archaic H. sapiens. Did I pick that off correctly?

Comment #136329

Posted by mplavcan on September 30, 2006 8:13 PM (e)

Nick:

Gotta run some errands tonight, so I can’t comment extensively, but the chart is exactly the point to make. As a note, I wasn’t taking issue with you, but only with one assumption of De Miguel and Henneberg.

You will note that the most obvious inflection is between early Homo and H. heidelbergensis. At that point, not only does brain size change, but relative brain size changes too (there are pubs on this, but I’m at home and don’t have the refs at my fingertips – I’ve seen the material, and it’s real). For our creationist friends, the transition along the Homo lineage is quite gradual. Even people who eat sleep and live these things have trouble finding a clean demarcation. This is one of the strongest cases of a non “punctuational” transition out there (but there are others, cf Cantius, Omoyids, Hyopsodus, Hyracotherium etc.). Great job.

Comment #136338

Posted by mplavcan on September 30, 2006 8:53 PM (e)

Mr. Heywood:

Huh? OK, let’s just ignore the bullock brains comment, which makes no sense at all in this Universe. Has it occurred to you that those of us in the profession have not asked these questions? Do you actually assume that we are THAT stupid? The issue of morphological divergence and speciation has been extensively investigated, and continues to be an active area of investigation.

To give you an idea (if you are even interested in hearing it), you can divide the investigations between those looking at phylogentic distance (relatedness), morphological and ecological divergence, and those documenting temporal transitions in the fossil record. Both are well known. Of particular interst for this thread, there are a number of well-known transitions in the fossil record for a diversity of morphological features. Just go to a library (thing with books and journals), and look in such things as Paleobiology, Paleontology, the the Journal of Vertebrate Paleontology, and a multitude of publically available paleontology edited volumes covering the topic. Please, it’s actually kind of fun.

Comment #136357

Posted by Richard Simons on September 30, 2006 10:28 PM (e)

Mr. Heywood,

O.K., do some other species by way of comparison to find out what this data means in terms of speciation. E.g., Run all the permutations & combinations on cranial capacity in donkeys and horses and see whether we can’t “prove” that dankeys are evolving into horses.

Do it yourself. Although as you drag permutations and combinations into a discussion involving regression and correlation I doubt if you have the expertise.

Comment #136359

Posted by Anton Mates on September 30, 2006 10:30 PM (e)

Philip Bruce Heywood wrote:

Incidentally, a bullock has a brain that we can make a meal from, but only desperate men make a meal from an entire crow - which comes in more intelligent than any bullock.

Crows are, of course, much smaller than bullocks. And they’re actually good to eat, though I don’t wish to encourage that. Kevin McGowan says they taste “kind of like blue jay,” if that’s helpful.

Comment #136366

Posted by waldteufel on September 30, 2006 10:58 PM (e)

Click on Mr. Philip Bruce Heywood’s name on his posts, and you will be taken to a website that shows what a wacko his is. I wouldn’t engage him in intellectual debate, because he should not be distracted from getting back on his medication.

Once again Nick, thanks for your thought provoking graphs.

Comment #136373

Posted by Anton Mates on September 30, 2006 11:24 PM (e)

Oh, I’ve seen the website. I can’t tell you exactly what was on it because my visual cortex and frontal lobes started fighting with knives afterwards, but I have seen it.

Comment #136402

Posted by djlactin on October 1, 2006 1:14 AM (e)

aha! I was right!

I tried to post this earlier, on the previous post, but was rejected. Here is my post verbatim.

Great chart, Nick.

1) Suggest you use EXCEL options to put trendline, equation and r² on it. (Click on chart, select Chart menu, etc.)

2) Stating up front that I am an evolutionist and a Ph.D (in… wait for it… Biology!), and have considerable statistical experience (taught at junior college level for 5 years).

But…

At the risk of providing an ‘out’ for the adversaries, charts like this that pool data from many species, can conceal considerable ‘internal’ information. The true trend COULD be a series of punctuation events, with the resulting lineages persisting and overlapping. (A series of overlapping horizontal lines.) Lumping the data without reference to species names would obscure such leaps and (erroneously) cause us to see continuity.

For example, my eyes see a strange pattern of perhaps 2 ‘leaps’ in the graph: CC was relatively low (ca. 500mL) and increased slowly (if at all) until about 2 MYa; At that point there is a sudden increase in variability, and the trend after about 1.5 MYa seems to emerge from the high end of this range of variability; this second part remains relatively flat until about 50kYa, after which the slope skyrockets. One possible explanation is that there are 3 separate lines here: a flat one from the beginning to about 1.5 MYa; another flat one from ca 2 MYa to ca 50kYa, and a third from 50kYA to now which increases quickly.

I’d be interested in discussing this perception. Does anybody else ‘see’ this? And if its real, how (if at all) are the breakpoints that I “see” correlated with species transitions in the fossil record?

Now I see that my perceived lower section was Australopithecins, the time of increased variability corresponds to the origin of Homo, the second section was H. erectus, and the final was H. sap.

Comment #136418

Posted by Torbjörn Larsson on October 1, 2006 3:52 AM (e)

Ooo, pretty colors! Yes, this is going to be the creo diagram.

Really interesting that it is hard to see neandertal larger cranial capacity here. It seems mostly to follow sapiens when eye-balling. (The best statistic method there is - no pesky numbers to falsify ones ideas. :-)

Following ‘splitters’, two of the three of four color-suggested groups with long record start out flatter and increase in the end. (Again pounding my naive expectation of a power relation from complexity and/or selfsimilarity instead of an exponential.)

Comment #136436

Posted by Philip Bruce Heywood on October 1, 2006 5:42 AM (e)

Jings, Anton, by the sounds of it, you get a similar reaction to www.creationtheory.com as you get to NEW SCIENTIST. Dangerous, allright, this up-to-date stuff. Was it you that was telling us that Species does not carry the implication, Special, or was that Larson Toejam or another of the Reference Committee? I went to look up Species afterwards, and couldn’t find it. Then someone told me that in some dictionaries it isn’t an entry in its own right. It is found under, er, guess which word?
Can’t say I’m acquainted with Kevin McGowan. He has an intrepid cuisine. Shag and crow I haven’t tried. My regards to him, but tell him, will you, that he should listen more to some of the people at T/O. He made a mistake. That crow he told you about tasted like blue-jay because, would you believe, it WAS blue-jay! There’s a continuous gradation between crows, blue-jays, and various other avian forms, such as the no-bul bul bul. Lots of the latter have been observed flocking towards T/O!

Comment #136467

Posted by Blorf on October 1, 2006 7:19 AM (e)

Should this be submitted to TalkOrigins, or do they not have the FTP space for so detailed a debunk?

Can I have some of what Heywood’s having? I’m in pain and he is very obviously not….

Comment #136485

Posted by Bob O'H on October 1, 2006 8:59 AM (e)

djlactin - To me it looks like you’re overinterpreting the plot (don’t worry, you’ve in good company. Sewell Wright did the same with some moth data). I’ve just drawn the plot on the log scale, and I can’t see a pattern.

I think what’s causing this is the gaps along the X axis, which splits the curve (which has an increasing slope) into segments, and you try to see each part as following a straight line. But the gaps accentuate this. This may also be informative about the way that the specimins are split into taxa, but I’ll have to look at that more carefully…

Bob

Comment #136494

Posted by Xris (Flatbush Gardener) on October 1, 2006 9:59 AM (e)

One striking visual pattern is the vertical lines: Clusters of data at “specific dates” like 2.5 mya. I presume that these are nominal dates for the ages of the fossils, but also that there’s some range of uncertainty, or margins of error, in the dating. If horizontal lines or bars or another representation than points were used, I wonder of the “gaps” would disappear?

Comment #136521

Posted by dr.steveb on October 1, 2006 11:48 AM (e)

Wonderful.

It might be educational and/or interesting to put in modern great apes such as the Chimpanzee species, other relatively intelligent current species (dolphins, dog, and of course octopus).

Also, the male/female issue is going to come up; female lower on average mean and median, with of course large overlap. Is “correcting” for body height and/or BMI of any utility and validity?

Comment #136524

Posted by Anton Mates on October 1, 2006 12:16 PM (e)

Philip Bruce Heywood wrote:

Jings, Anton, by the sounds of it, you get a similar reaction to www.creationtheory.com as you get to NEW SCIENTIST.

Oh, not at all. Like I said before, New Scientist is great reading if you want to write about science for comic books. Not a peer-reviewed scientific journal, of course, and it tends to uncritically cover all sorts of pseudoscience, but still quite entertaining. With creationtheory.com, on the other hand…well, how is anyone supposed to expose their mind and soul to this or this and walk away alive and sane?

I did manage long enough to note that you’ve apparently done some ranching. Ever heard of a beefalo?

Was it you that was telling us that Species does not carry the implication, Special, or was that Larson Toejam or another of the Reference Committee?

Wow, even your choice of targets for ethnic mockery is outdated.

I think that was both of us. But everyone here who knows anything about either biology or Latin was thinking it.

I went to look up Species afterwards, and couldn’t find it. Then someone told me that in some dictionaries it isn’t an entry in its own right. It is found under, er, guess which word?

Wait, you have a dictionary which doesn’t have an entry for the word “species”? Does it by chance have cardboard pages and big letters?

Can’t say I’m acquainted with Kevin McGowan. He has an intrepid cuisine. Shag and crow I haven’t tried. My regards to him, but tell him, will you, that he should listen more to some of the people at T/O. He made a mistake. That crow he told you about tasted like blue-jay because, would you believe, it WAS blue-jay!

Almost there! It tasted like blue jay because they’re very close relatives, both belonging to a sub-clade of the Corvidae.

“Nothing in gastronomy makes sense except in the light of evolution,” as Dobzhansky said after missing lunch once.

Comment #136531

Posted by RBH on October 1, 2006 1:58 PM (e)

Torbjörn Larsson wrote

Really interesting that it is hard to see neandertal larger cranial capacity here. It seems mostly to follow sapiens when eye-balling. (The best statistic method there is - no pesky numbers to falsify ones ideas. :-)

I think that’s called the Inter-Optic Trauma test – does something hit you between the eyes?

RBH

Comment #136543

Posted by David B. Benson on October 1, 2006 3:30 PM (e)

Xris, the deeper the time, the bigger the error bars. The 2.5 million year date is a nominal one. I don’t know what the error bars ought to be at that deep time, but your idea is a good one. Imagine error bars about a quarter of a million years on each side to see that, as far as there is good data now, there are no missing links.

Comment #136554

Posted by Mike on October 1, 2006 4:24 PM (e)

Really, excellent and thought-provoking stuff. I just hope that you had an ergonomic keyboard when you entered in the data set!

Anton Mates wrote:

Almost there! It tasted like blue jay because they’re very close relatives, both belonging to a sub-clade of the Corvidae.

“Nothing in gastronomy makes sense except in the light of evolution,” as Dobzhansky said after missing lunch once.

Interesting. I tasted crocodile a few months back, I thought it tasted like a cross between chicken and prawn. I wonder if it’s possible to make a phylogenetic tree based entirely on the way that animals taste! Perhaps it should be added to the “29+ ‘evidences’ for evolution”?

Comment #136562

Posted by B. Spitzer on October 1, 2006 5:14 PM (e)

Mike asked:

I wonder if it’s possible to make a phylogenetic tree based entirely on the way that animals taste!

This rang a dim bell in my dim memory. Google “‘tastes like chicken’ phylogeny”. The third hit is a relatively large Powerpoint file. Open it and go to the final slide.

Interestingly, humans are classified as “taste like pork”.

More Spam, anyone?

Comment #136590

Posted by Henry J on October 1, 2006 7:12 PM (e)

I’m pretty sure there was a discussion here of heritability of taste a while back? (Either here or on AtBC?)

But I can’t seem to find it offhand.

The upshot, iirc, is that “tastes like chicken” originated in early tetrapods, and got inherited by any subsequent lineage that didn’t evolve its biochemistry in some other direction since then.

Henry

Comment #136613

Posted by Torbjörn Larsson on October 1, 2006 8:39 PM (e)

“I think that’s called the Inter-Optic Trauma test – does something hit you between the eyes?”

:-) That happens to me a lot. (Not least in the physical sense, since as I mentioned on the other thread I am wide between my eyes. ;-)

It happened here too. This time Nick mentioned a paper on the original thread where they put as the (later confirmed) null hypotheses “that the changes over time are a result of one process”. With that framing, my wild speculations on power relationships seems a lot more demanding, disregarding the lumpers vs splitters ideas. Now I also think the exponential relationship is the most natural one.

Comment #137018

Posted by windy on October 3, 2006 10:23 AM (e)

Really interesting that it is hard to see neandertal larger cranial capacity here. It seems mostly to follow sapiens when eye-balling. (The best statistic method there is - no pesky numbers to falsify ones ideas. :-)

Remember that Neanderthal brain is only said to be larger than the modern human brain, not that of Paleolithic H. sapiens (afaik).

Comment #137176

Posted by djlactin on October 4, 2006 2:05 AM (e)

I have added trendlines for each species to the graphs (it’s easy to do, a simple EXCEL function). What I found is that the brain volume increases over time for each lineage for which time-duration is sufficient, and that the lines are remarkably parallel (roughly 125 mL/MY) except for Neantertals (nearly 1700 mL/MY [!!]), and modern H. sapiens (350 mL/MY). Note that time coverage for the last two is comparatively short.

In brief: the Australopithecus spp. sit roughly on one slowly-rising line; the H. habilis line is parallel to this but jacked up by about 200mL within the interval of overlap; the H. erectus line is roughly parallel to this but jacked by roughly another 300mL; The archaic Homo line is parallel to this but jacked up by about 300mL more. The H. sapiens line is about 300mL above this.

The trend is for up-sloping lines which overlap in time, with each line about 250-300 mL higher than the preceding one during the interval of coexistence. (Except for the extremely anomalous neandertal lineage.)

This apparent quantization of line elevations can be interpreted 2 ways:
1) The trend in increasing brain size shows several saltation events of about 250mL magnitude
OR
2) fossil hominin taxonomy is based on brain volume and 250 mL is the minimum value for declaration that 2 populations are ‘in fact’ 2 species.

I’d post the graph but it’s Nick’s baby.

Comment #137510

Posted by Jeffrey K McKee on October 5, 2006 8:11 PM (e)

Brain size is interesting and informative, but it is brain size for body size – encephalization – among mammals that really matters.

Many mammals have become more encephalized in the Pliocene/Pleistocene, including humans, horses, and baboons. Others have not (e.g. most carnivores, rodents, bovids, etc.) But even if one did a plot of encephalization quotients (EQ), only hominins have had a dramatic and continuous growth of the EQ.

Especially considering other evolving traits of the hominins, there ain’t no stasis, and their ain’t no punctuation. The debate over H. habilis vs. A. habilis is simply one of nomenclature that demonstrates how fuzzy the transition was … no big leap.

On the other hand, the exponential transition of hominin brain size took, say 3 million years. That is a much shorter timespan than the “Cambrian Explosion,” and thus in the vastness of geological time, could be considered to be a punctuated event.

Cheers,
Jeff

Comment #138259

Posted by Nick (Matzke) on October 9, 2006 5:41 PM (e)

Heh, this blog has now been mentioned on a spanish language blog:
http://memecio.blogspot.com/2006/10/aumento-gradual-de-capacidad-craneal.html

Comment #138409

Posted by Henry J on October 10, 2006 10:28 AM (e)

No hablo español!