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 A105 Human Origins and Prehistory
A105 Early Homo Activity
 

1.  Look at the teeth of A. boisei and compare to the teeth of OH 7.  What do you notice about tooth sizes?  What could this indicate about the behavior of these two hominids?

  A. boisei has much larger molars than OH7, a representative of early Homo.  The molars are also very large compared to the incisors in boisei.  This could indicate dietary differences, with boisei concentrating on hard foods that require a lot of grinding, while OH7's diet may have required more use of the front teeth.  OH7's smaller molars could also indicate that this hominid performed more of its food preparation outside the mouth, using its tools.

2.  The next few questions will relate to KNM-ER 1470 and KNM-ER 1813/OH 24.  If these are from a single, highly dimorphic species, what sex would you guess each one to be?

If 1470 and 1813/OH 24 are members of a single, highly dimorphic species, 1470 would be the male and 1813 the female -- in all primates that show sexual dimorphism, the male is the larger sex.

3. Look at the skull vault (braincase) of the two specimens.  What differences do you notice? (Think about size, shape, brow characteristics.)

1470 has a larger braincase than 1813/OH 24 (in fact, the cranial capacities are 770 cc and 600 cc respectively).  Also, the 1813 skull is more globular (rounded) and has a brow ridge; 1470 is longer and a bit flatter without a brow ridge.

4. Look at their faces and teeth (sockets, in the case of 1470).  Briefly describe each, focusing on the differences. (Think about the nose, tooth size, facial prognathism and shape, etc.)

 1470 has a taller face, with flat, squared zygomatics; the face is almost dished as seen in robust australopithecines.  It has no bony nose, and it has substantial prognathism (face projecting out in front).

1813/OH 24 has a smaller face, with less prognathism.  Its zygomatics recede back instead of being squared and flat.  1813 also has a small bony nose.  Its molars are smaller than those of 1470, and its incisors appear larger.
 

5. Compare the postcranial information (ER 1472, 1481 casts and photo; OH 62 photos).  What do you notice?

OH 62 is a much smaller hominid.  Its femur would be closer to A. afarensis in length than to ER 1472 or 1481.  Also, its arms are long in relation to its legs, and its fingers are curved.

6.Using the information you have about these two specimens, would you consider the two fossils to come from two species or one?  Why?

If we look at the pattern of sex differences seen in highly dimorphic modern primates such as the gorilla and orangutan, we can get an idea of whether the differences between 1470 and 1813 are compatible with what we would expect in a single species.  As explained in today's lecture notes, the differences are either more than you would expect to find in a single species (brain size, teeth) or backwards with regard to sex (browridge, bony nose).  So, it appears that these two specimens represent different species.
 

7.  What has changed in H. erectus (KNM-ER 3733) with respect to early Homo? You can use either 1470 or 1813, but be sure to note which you choose.

3733 vs. 1813                      3733 vs.1470
3733 has:                               3733 has:
   larger brain                            brain only slightly larger
   larger incisors                        reduced face (zygomatics not squared off)
   taller face                              smaller molars
   slightly larger molars              reduced prognathism
   entirely human body proportions
     (unlike OH62)

                           3733 differs from both 1813 and 1470 in that it has a larger nuchal area and its incisors are increased in size compared to its molars.