Zoology 445
Fall 2006
8 December
Human Evolution: Handout
Reading: This chapter covers more material than I expect for this course. The test will only cover the
following:
1. Pages 727 to 738 (stopping at Fossil Evidence.
2. Skip the material on fossil evidence.
3. Continue reading at the last paragraph on page 745 and end at 759.
Start with...
I. The Primates
A. Evolutionary relationships within the Catarrhini.
1. Classification - Figure 19.1
B. The position of humans in the African Great Apes & Humans has been debated for nearly 20 years.
Consensus now reached that true relationship has chimps and humans being the closest relatives. Figure 19.3
Consensus:
Morphology:
11 of 14 phylogenies based on different
independent genes support this tree.
AM Jarosz
2 of 14 molecular phylogenies support this
tree.
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1 molecular phylogeny supports this tree:
Gene trees versus species trees. Example: Fig 19.5
Therefore, the gene tree need not always mimic
the species tree.
Last common ancestor between humans (genus Homo) and chimpanzees (genus Pan) was about 5 MYA. (See
Fig 19.2 & 19.6)
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II. The Human Lineage
1. Bipedal gait
a. Allows us freedom to use our hands for tool use.
Note arm to leg ratios:
Knuckle walking > 1.0
Bipedal < 1.0
Note point of attachment of head on spinal
cord.
2. Big brains
A. Phylogenetic relationships - Fig 19.16b
Traits in the phylogeny.
Group
Chimps & Gorillas
Ratios in A. afarensis
All other Austrolrpithecus
Humans
Brain size:
3
Arm to leg ratios:
1.10
>1.0
<1.0
0.90
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III. Origin of our species, Homo sapiens.
Four hypotheses:
African Replacement and Multiregional have received the most attention, because they predict very different
patterns of phylogenetic relationships among the races.
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New species described in 2004 issue of Nature.
Nature 431:1055 (2004) Paper posted on course web site.
Homo floresiensis Nicknamed the “Hobbits”
 Short (3ft tall), Small brains (380 cc; modern humans 1400cc), but upright gait
 Lived as recently as 13,000 YA
 On island between Java and Australia
Controversy on whether it is a new species or diseased H. sapiens. If it is a new species, its place in the
phylogeny is unclear
\Evolution Zol 445\2006\ Human Evolution Notes.doc
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