Re: Brain size, IQ

Gerold Firl (
5 Sep 1996 19:41:33 GMT

In article <>, Ralph L Holloway <> writes:

|> 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.

The indonesian solo skulls were only 130,000 years old? That would
provide significant overlap with archaic h. sapiens in africa.

I have tried to estimate human genetic diffusion time, using very
crude assumptions and modelling, and I get very short periods of time;
something on the order of 10,000 years for genes to diffuse from one
end of the old world ecumene to the other (say, zimbabwe to java). To
me, the out-of-africa model of bands of h. sapiens migrating
throughout the old world and displacing more archaic humans is clearly
flawed; the anatomical continuity between modern populations and their
pre-h. sap predecessors is enough to show that local populations have
deep roots.

In any case, h. sap genes would have diffused throughout previous h.
erectus populations before any large-scale migrations convected them.

|> > 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.

Yes; I'm not sure where I got that number.

Any idea about pre-h. erectus cranial capacity? How big was an h.
habilus brain?

|> > 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?

Over the long run, it seems like a safe assumption; archaic h. sap
populations of 150,000 b.p. with cranial capacities averaging 1200 cc
were probably less intelligent than modern humans.

I have also read that modern east asian populations have the highest
cranial capacity/body mass ratio among current humans, and they also
have the highest IQ's. The possibility of a causal link can not be
ruled out.

Disclaimer claims dat de claims claimed in dis are de claims of meself,
me, and me alone, so sue us god. I won't tell Bill & Dave if you won't.
=-=-=-=-=-=-=-=-=-=-=-=-=-=---- Gerold Firl @ ..hplabs!hp-sdd!geroldf