Re: Brain size, IQ

Ralph L Holloway (
Tue, 3 Sep 1996 22:37:10 -0400

On 3 Sep 1996, Gerold Firl wrote:

> I used that data because I happened to have it on hand. The trend is
> present for all the hominid species: cranial capacity increases with
> time. Archaic h. sapiens had a cranial capacity of about 1200 cc, just
> like late-model h. erectus. That has increased 25% to the modern size
> of 1500 cc over the last 200,000 years or so. (This is from memory, so
> my numbers are a little vague.)

For whatever it is worth, here follows some recent compilation of these
fossil hominid brain volumes: from Indonesia, HE 1, 953;HE2 ,815; HE 4,
900; HE 6, 855; HE7, 1059; HE 8, 1004; Sambun17, 1035. The mean = 945.8.
The Chinese from Z11, 1030; Z3, 915; ZV, 1140; ZVI, 850; ZX, 1225; ZXI,
1015; ZXII, 1030; Hexian, 1025. Mean = 1028.75. Lantian 2 is 780, which I
would place more toward the indonesian time frame. Indonesian Solos:
SoloI, 1172;Solo V, 1250; SoloVI, 1013; Solo IX, 1135; Solo X, 1231; Solo,
XI, 1090. Mean = 1148.5. So the progression is from Indonesia (1.6 MYA?)
945.8 to China (about .6-1 MYA?) 1028.75, to Indonesia (abt .13 MYA?) at
1148.5. These values are CC's or ml's, and I 've had the honor of doing
the endocranial casts from Indonesia and Solo, and feel confident about
the values. Postcranial remains are very scarce, but I doubt sincerely
that the increases seen in these averages would be related to some
allometric relationshiop between brain size and body size. The increase is
most probably related to increase in brain volume without selection
operating on body size. Most of these values can be found in the
Encyclopedia edited by Delson, Tattersall, and Van Couvering, published by
Garland Press around 1991? Under Brain. I wrote the article, and a newer
edition is being edited currently, with all the hominid endocranial

> This trend is clearest for erectus, which started with a much smaller
> brain; I believe early versions weighed-in at around 700 cc. You had
> claimed that cranial capacity did not increase over time within a
> single species; I was pointing out that you are misinformed. The data
> from zhoukoudian actually understates the magnitude of the trend, since
> erectus spanned about a million years.

The earliest erectus is possibly Lantian, not calculated in the above,
although the KNM-ER 3733 (848) and KNM-ER 3883 ( 804) H. erectus (or
ergaster if you prefer) are well above 800, particularly if OH 9 (1067)
and KNM-WT 15000 (900) are combined as erectus: mean = 904.75ml. This is a
fair amount greater than the 700 mentioned above.

> Getting back to your claim that cranial capacity is not a hereditable
> trait, and all boggles aside, there is no anomaly: human intelligence
> is adaptive, and natural selection has produced successivly more
> intelligent humans. It has also produced larger brains.

Sure looks that way to me. Question is, can the same reasoning be applied
to within-species variation?
Ralph Holloway