KNM-ER 1470 is not a microcephalic

3 minute read

I keep seeing this story about Tim Bromage's "computer-simulated" reconstruction of KNM-ER 1470.

Bromage said his team's reconstruction includes biological principles not known at the time of the skull's discovery, which state that a mammal's eyes, ears and mouth must be in precise relationships relative to one another.
"It doesn't matter if you're a rat, a kangaroo, an elephant, a human or a dog -- their [facial features] are all organized to a very specific architectural plan," Bromage said.

Well, let's see. Here's the lateral view of the old and new reconstructions in the article:

Bromage reconstruction of KNM-ER 1470

The photo accompanying the article

Wow, that new reconstruction sure has a sloping face doesn't it? Oh wait! It's rotated at a different angle from the old reconstruction! Let's use Photoshop to fix that right up:

Bromage reconstruction of KNM-ER 1470

Same picture, with the reconstruction rotated to the Frankfort horizontal, like the old reconstruction.

Well, now, that's better. Now the vaults are at the same orientation. And the reconstruction does have a bit more sloping face. By about 5 degrees.

Now, a good cast of ER 1470 comes with the face and vault in separate pieces. There is only one join between them, at the nose, and it's not a very good one. Every graduate student in the world has probably taken these two pieces and rotated them back and forth to decide on the best angle. No doubt, there is five degrees of variation between them all. I'm perfectly willing to believe that the skull should have five more degrees of inclination to its face.

I wish that new reconstruction had the nasal bones pictured, though -- a greater slope makes the join there worse, which is probably why the original reconstruction was made with the more vertical orientation. Oh wait! It looks like the nasal bones have been crammed back under the frontal bone! That seems odd...considering the fronto-nasal suture is there underneath the small browridge. Hmm...

I think this particular issue is one for which more detail will be necessary. That seems like an unreasonable placement of the nasal bones, but we only have the one view to work with.

There is a lot of talk about the brain size of the specimen. I don't have any details of the presentation, and it is possible that Bromage was incorrectly quoted. Here is what the article says:

The new reconstruction suggests H. rudolfensis' jaw jutted out much farther than previously thought. The researchers say the cranial capacity of a hominid can be estimated based on the angle of the jaw's slope and they have downsized KNM-ER 1470's cranial capacity from 752 cubic centimeters to about 526 cc. (Humans have an average cranial capacity of about 1,300 cc.)

That, of course, is utter nonsense. Ralph Holloway produced an endocast, the joins between the fragments are good, and the volume of 752 cc was measured by water displacement. Why in the world would you estimate brain size from the face when you have a perfectly good vault? It has to be a misquote.

The article quotes Bob Martin as a skeptic:

"What they're claiming is you stick the face out, and because the face sticks out more the brain capacity has to be less. I don't follow that at all," said Martin, who is an expert on hominid skulls and who was not involved in the study.
"They haven't changed the skull at all; they've simply rotated the face outwards," Martin added.

He mentions that the 752 cc estimate is not a problem in comparison to other contemporary hominids. We can also mention the Dmanisi crania, the largest of which (D2280) has a brain size essentially the same as KNM-ER 1470, at 1.75 million years. KNM-ER 1470 is one of the most solid endocranial volume estimates in the fossil record. It's the face that's crummy!