Week 3: 2.5 - 1.5 mya: Enter Homo

Review: possible advantages of obligate terrestrial bipedalism:

1. ability to carry meat or other food items to trees or
other refuges, or to mates for provisioning;
discussion of Lovejoy model
2. reduction in skin area exposed to direct sunlight,
decreasing heat stress
3. freeing of hands for tool use
4. decrease in energy required to walk at
normal (low) speeds
5. ability to see over tall vegetation during passage
from place to place
6. ground doesn't break (i.e., hominids getting too
big for arboreal adaptation?)

Bipedalism provided the basis for two distinct
hominid adaptations, diverging 3.0-2.5 mya:

1. > cheek teeth for coarser vegetal foods
(A. boisei in E. Africa & A. robustus in S. Africa)
2. > brain size, > use of tools, & > meat eating
africanus > H. habilis/rudolfensis > H.
ergaster/erectus)
3. Uncertainty remains as to whether A afarensis is
ancestral to both lines; or there may be two species
within "A. afarensis"

I. Early Hominids, Continued: Into the Pleistocene
Enter Homo, beginning with H. habilis/rudolfensis  2.4
mya. From A. africanus? Known from E. Africa. habilis
variable & problematic as a taxon.

A. enlargement of brain (to mean 630-700 cc)
B. meat eating (cut marks on bone 1.8 mya)
C. manufacture of stone tools

1. emphasis on flakes rather than cores in
Olduwan industry, appearing 2.4 mya
(Omo, Ethiopia). Relatively nonselective use
of stone. Hard-hammer percussion domin-
ant technology. Some transport & curation
of stone. Shift towards use of more animal
resources in opportunistic foraging pattern
still dominated by plant foods during
dessication of 2.5 mya

a. sharp unmodified flakes most efficient
for opening carcasses
b. for scavenging dried meat from carcasses,
large flakes or sharp-edged cores work
best
c. for cracking bones for marrow or opening
skulls, unmodified cobbles of heavy cores
are best
d. When use-wear can be seen, animal
butchering, woodworking, and cutting
soft vegetation are dominant activities (in
that order) on flakes

II. Homo erectus (partial remains, identification
uncertain) dated (in 1994) to 1.8 - 1.6 mya in Java
(Swisher) from Dmanisi in Georgia at 1.8 mya;
and 1.9 mya in Longuppo Cave, Sichuan Prov-
ince, China with very crude stone tools (Huang);
some uncertainty in all these dates, however. [At
Ngandong, Java. H. erectus may have survived
till 40 kya or later! (Swisher)]

A. "Turkana boy" northern Kenya, 1984, 1.6 mya;
first considered H. erectus, now typically called
H. ergaster; essentially modern body structure,
very tall, big brain relative to predecessors.
a. more use of bifaces by 1.5 mya, roughly
contemporaneous with appearance of H.
ergaster marks appearance of Acheulean
industry: very effective for butchering large
animals
B. beginning with ergaster/erectus, leap in body
size & decrease in sexual dimorphism.

III. What about "Culture"? (Boyd & Richerson):
"information capable of affecting individuals'
phenotypes which they acquire from other
conspecifics by teaching or imitation." (Nongenetic
transfer; social learning) and Language?

IV. Controversies surrounding early Homo

A. habilis: is it a valid taxon, and what should go in
it?
B. Significance of brain enlargement. Metabolically
costly.
C. Hunting vs. scavenging as source for meat.
D. Importance of "provisioning" and of home bases.
E. What the changes in stone tools moving from
habilis to erectus reveal about the mental abilities
of early Homo
F. Radiation and its timing.

syllabus