BIO 358 Lecture 9: BIO 358 Topic 9
14 Jun 2018
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Topic 9: How and when we became human – fossil record 2
Key Terms:
1. Paleoanthropology: refer to topic 8
2. Hominids: refer to topic 8
a. australopithecines: australopithecus afarensis and africanus
b. “humans”: homo erectus, habilis, rudolfensis and heidelbergensis
c. nariokotome boy (homo erectus)
d. lucy (australopithecus afarensis)
3. Postcranial skeleton: Refers to the entire skeleton other than the head. The prefix post is used instead of
sub because most animals are quadrupeds and, thus, their non-head skeleton is behind rather than under
their heads. As bipeds we are the exception rather than the rule among mammals. It will be very convenient
to talk separately about the evolution of the head and of all the rest of the skeleton – the postcranial skeleton
– as two separate units (Chapter 7).
4. Gluteus maximus: This sizable human buttock muscle is the largest single muscle in our bodies. It is
dramatically enlarged relative to the same muscle in chimps. This has been interpreted as an adaptation to
bipedal locomotion in humans; however, its enlargement is probably more likely to be part of the elite
adaptation to high momentum throwing in humans (Chapter 7). Also see muscles.
5. Latissimus dorsi: see muscles.
6. Pelvis: The large bowl-shaped hip bone to which the legs (femur) and the base of the spinal column attach.
This bone is very different in us than in our closest living relatives, the chimp. These differences tell us about
the evolution, first, of bipedal locomotion and, second, of uniquely human elite throwing (Chapter 7).
a. ilium and iliac crest: The ilium is the large blade-like portion of the pelvis (see images in
Chapter 7). The iliac crest is a thickening along the top of this bone. The ilium represents the
attachment point for the gluteus maximus and the iliac crest for the so-called oblique muscles. The
placement of these muscle connections has apparently been moved in humans relative to our last pre-
human ancestors as part of our adaptation to elite aimed high-momentum elite throwing (Chapter 7).
7. Femur: The thigh bone. It has a ball joint at the top or head which fits into a socket in the pelvis. This joint is
very informative about the walking and throwing behaviors of its owner (Chapter 7).
8. Oblique muscles:
Muscles: Large bundles of tissue that actively contract when appropriate nervous system commands
are received. Most muscles span joints between bones and cause the joint to close (flex), open (extend), or
twist. Muscle bundles can only do two things -contract and relax. Relaxation is passive while contraction is
active. Thus, when a muscle relaxes, the joint either snaps back to its resting position or is pulled through its
resting position and beyond in the opposite direction by the active contraction of opposing muscle bundles.
The fine control of complex, opposing sets of muscle bundles by our central nervous systems is what allows us
to move with grace, power, and control.
The attachment points of muscles on bones and the joint faces between bones are often preserved in
fossils allowing us to learn a great deal about the behavioral/movement capabilities of ancient animals,
including our own ancestors (Chapter 7). The following individual muscles torque the body (or control its
torqueing) during the elite human throwing motion. Their placement and structure can be found in the Figures
in Chapter 7: latissimus dorsi, obliques (internal and external), tensor fascia lata, gluteus maximus and
peroneus longus. The dorsal interosseous is an important hand muscle involved in throwing (Figures in
Chapter 7).
9. Scavenging: Refers specifically in this context to a life style based on eating the remains of the kills originally
made by members of other species who are generally professional carnivores. Many vultures are scavengers,
for example. There is reason to believe that our most immediate australopithecine ancestors, possibly
including Australopithecus garhi, were scavengers. If scavengers use threat to scare carnivores off their kills,
they are sometimes referred to as power scavengers. A very attractive hypothesis for the original selective
pressure leading to the evolution of elite throwing proto-humans was adaptation to power scavenging by an
Australopithecus garhi-like ancestor (Chapter 7).
10. Stone tools:
a. oldowan: This name is derived from the Olduvai Gorge in East Africa where the original
examples of these tools were found by Lewis and Mary Leakey. The early forms of these tools are very
simple, consisting of stone flakes used for sharp edges and rounded stones probably used for battering
and throwing, including manuports. Early members of Homo (possibly including Homo rudolfensis
and/or early Homo erectus) may have made early Oldowan tools. Oldowan tools might also have been
made by Australopithecus garhi and by the Dmanisi Homo erectus individuals (Chapter 7).
b. acheulean: This set of stone tools was initially produced by Homo erectus beginning around
1.6 million years ago. They include the hand axe, an elaborately crafted bifacial cutting, boring, and
chopping tool, resembling a giant stone arrowhead. These tools require sophisticated manufacturing
techniques and are far beyond the capabilities of non-human animals. However, they are much less
sophisticated than those made later by behaviorally modern humans (Chapter 11). Moreover, these
tools continued to be made in essentially unchanged form for well over 1 million years by early
humans! Such a period of adaptive stasis is profoundly foreign to us today as modern humans.
KEY CONCEPT QUESTION: In the TOPIC 9 lecture and in Chapter 7 in Death from a Distance we explored the
question of when elite human throwing first evolved and its temporal relationship to other details of human
evolution. The theory we are exploring makes a very specific prediction about what this timing and these
relationships should look like – predictions that the fossil record confirms.
Which of the following is the most accurate description of the timing of elite throwing evolution and its
relationship to a key event in human evolution?
a. Elite human throwing evolved around 2-2.2 million years ago, immediately preceding the first indications of
uniquely human social cooperation.
b. Elite human throwing evolved around 6 million years ago, much after the divergence of the human and
chimp lineages.
c. Elite human throwing evolved around 500,000 years ago, following the evolution of unique patterns of
human hunting.
d. Elite human throwing evolved around 100,000 years ago, immediately preceding the fossil indications of
human speech.
Notes:
1) How and when we became human—fossil record 2
a) We looked at evolutionary history from when we diverged from chimps
i) ~6m years old
ii) contrast to human written history (5000) years old
b) We talked about how we can read 6m year history using tools of fossil record
i) How these fossils are formed, how we date them
(1) Relative vs. absolute age
ii) How detailed and specific they can actually be
(1) Endocasts of human brain (the cast fill thingy)
c) Climate change and what happened in Africa
i) ~20mya, rainforest relative to savanna was slightly larger
ii) Now, shrinking rain forest and growing savanna
iii) Concept where our ancestors emerged → larger rainforest to smaller, larger savanna
d) Looked at only bipedal ape portion of our ancestry
i) Australopithecus: southern ape
(1) They were bipedal, relatively small brains
ii) 2mya, scientists score the difference between the two is by brain size (~2mya)
(1) where humans emerged being bipedal like australs, however, with a larger brain
(2) Looked at difference in these brains, timing was ~2mya and use that as a proxy for the human
village
(a) Human village would have emerged right at that arrow from my lecture 8 notes (2mya
mark)
e) So when would elite aimed throwing emerge?
i) Predict that it comes immediately BEFORE emergence of human village and larger brains
f) What are we saying/not saying?
i) NOT saying large brains or some sort of cognitively gifted brain is the CAUSE of human uniqueness!
(1) not denying that humans have larger brains, not denying that we are cognitively gifted in
certain ways, but we’re saying that it is not causal, simply an effect.
ii) ONLY using the fossil of a large brain to time expanded human non-kin social cooperation THUS
time to emergence of the HUMAN VILLAGE!
(1) Human village itself couldn’t leave a footprint
(a) Only footprint it could leave is the large brain
g) Why the village?
i) If there is: NO management of non-kin COI: NO extended non-kin social cooperation to start with
→ means we don’t have a human village
(1) If we don’t have a human village → NO SELECTION for large, resource-expensive brains, NOR
can they be sustained!
(a) Large brains are EXPENSIVE: NEED THE HUMAN VILLAGE FIRST
(i) we are using the brain to be the proxy for the human village
h) Be careful not to mix up the cause and effect.
i) CAUSE: Management of conflicts of interest
(1) EFFECTS:
(a) Human village
(b) Selectin for large brains
2) Post-cranial skeleton in australs and early humans and how that change came about for elite aimed
throwing
a) Non-human social cooperation
i) Dominated and limited by COI
