The Perspective from Africa – Job Kibii: Australopithecus in East and South Africa

The Perspective from Africa – Job Kibii: Australopithecus in East and South Africa

August 31, 2019 2 By Stanley Isaacs


(air whooshing)
(beeping) (soft piano music) – [Narrator] We are the paradoxical ape. Bipedal, naked, large-brained, long the master of fire,
tools, and language, but still trying to understand ourselves. Aware that death is inevitable,
yet filled with optimism, We grow up slowly. We hand down knowledge. We empathize and deceive. We shape the future from our shared understanding of the past. CARTA brings together experts
from diverse disciplines to exchange insights on who we are and how we got here. An exploration made possible by the generosity of humans like you. (calming music) (upbeat music) – Good afternoon. I would like to start
with acknowledgements, just in case I run out of time and Berhane kicks me out. I’m happy to be here and
thanks to CARTA Foundation for inviting me, and thank you to the organizers, Berhane Asfaw and Lyn Wadley, and also to Linda, I think we have been
communicating a lot with Linda. And also to the general staff of CARTA for making this trip and
this symposium a success. I’m saying a success because
I think it will be a success until the end, So I’ve been invited to give
a talk on Australopithecus in East and South Africa. It’s quite an enormous task, and I think I’ll try to do it justice because it’s an enormous field of research that has gone on to make this
research come to fruition. So let’s get the facts. For the first five million
years of our evolution, since our common ancestors
with the closest cousins, the chimpanzees, at seven million years. Those first five million
years of our evolution confined in Africa. So if we are understanding
the story of humankind, the story of us the very
first five million years, you don’t find fossils
anywhere except in Africa. And most of those fossils
that span during that time, they are within the group
called Australopithecus, the genus called Australopithecus. There are others which
I’ll talk about later, but since this is the focus of the topic I’ll confine myself mostly to that group or genus,
the Australopithecus. So to talk about the Australopithecus is, if you are talking about the genus it’s almost the same as
if you are talking about human evolution, you cannot
talk about human evolution without talking about Charles Darwin. If you are talking about Australopithecus you cannot talk Australopithecus without talking about Raymond Dart. This is the person who coined the term Australopithecus in 1925,
after getting a skull of what is commonly known as Taung child, in a site in South Africa called Taung. This was in 1924, but the publication to name
this species was in 1925. Raymond Dart recognized
various characteristics of the Taung child, some
of which were human-like and others that were ape-like. And as highlighted in
the slide you can see the Taung child’s skull possessed a forward placing foramen magnum, indicating that it was walking bipedally. And we know as part of the primate family, we are the only ones who walk bipedally. So he recognized that
this has to be in line with the humans. He also recognized that the
ape had a human-like forehead. It had no marked diastema, which is the space between
the canine and the incisors, and it also had a reduced brow ridge. That’s this part of your face. Those features tied it, or
brought it closely in line with what we see in humans. However, the skull itself
had a very small brain, which is ape-like. It had a jaw which was jutting forwards, which was also ape-like,
and it had no chin. So he called these
Australopithecus africanus, the southern apeman from Africa, and described it as an
extinct race of apes intermediate between
living anthropoids and man. However, this didn’t go down well within the scientific community. He was criticized first
for mixing Greek and Latin in coming up with the
naming of the species. Also at the same time,
we had the Piltdown hoax. which had been engineered since 1912. and it indicated that the humans, or the ancestors of humans, we should be expecting a big
brain and an ape like jaw, and the rest of the body was supposed to have been catching up, in evolutionary terms. And also it didn’t help
that during that time, Homo neanderthalensis had been discovered in Germany in 1856, Homo erectus had been discovered in Java in 1881, and Homo heidelbergensis had
also been discovered in 1907. So there are already specimens
that were already human-like, that were competing with the theory that Raymond Dart had indicated that Australopithecus
africanus was ancestral to the humans. And also because of the
small brain it was believed that the Australopithecus,
or the ancestors to humans, should have a big brain, and so Australopithecus
africanus was contrary to what the scientific
community believed at the time. But science has proved that, that was right and we now believe, there’s a general consensus, that Australopithecus
occupy a morphological space intermediate between early
members of genus Homo and the living African apes. Sometimes it’s much, Ardipithecus, which is there, and Kenyanthropus, here, early members of Homo
Paranthropus, which we have Paranthropus aethiopicus in East Africa, Paranthropus boisei,
also in in East Africa, and Paranthropus robustus in South Africa. They made these into the
genus Australopithecus, but this becomes too restrictive
because there are clear anatomical differences
between the four groups, and this presentation
does excludes members that are at any time referred
to as a Ardipithecus, Paranthropus, Kenyanthropus, and Homo, and restricts the
discussion on only members that have been referred
as Australopithecus and in East Africa and South Africa. In East Africa we have a number of species
that have been identified and these are the ones
that have general consensus that they are within the
genus Australopithecus. We have four species. We have the latest that have
been discovered in Ethiopia this is Australopithecus deyiremeda, I hope I’m pronouncing that right, Berhane can correct me. These Australopithecus
anamensis, discovered in Kenya. Australopithecus afarensis,
discovered in Kenya, Tanzania, and Ethiopia. Australopithecus garhi
discovered in Ethiopia. And the vertical lines indicates a species that have been found in more than one site, If it’s just a dot, like in garhi, indicates it has just been
found in just a single site. And the horizontal line indicates the span if it dates, their dates that extend from, let’s say, for example, for anamensis 4.2 through
3.9 million years. But if it’s just a
single dot that indicates that specimen has just one
single date associated with it. In South Africa we have
Australopithecus prometheus that was named in 1948. Then, kind of, it was
controversial whether that was, the specimens represented
a species, a new species and it was dropped off. But last year there were
discoveries that revived the name. It’s still controversial
whether it’s scientific to revive a name or whether the name should
have fallen out of use. And the dates are still
also controversial. we have dates that at
least at 3.67 million years and some who suggest that
the species, in fact, dates to less than 2.2 million years. So that’s why we have that dotted line. In South Africa we also have
Australopithecus sediba, at 1.97 million years, and Australopithecus africanus,
at 3-2.1 million years. While each of the species
has its own particular morphological characteristics,
time constraints do not permit discussing
each species in isolation, Instead I’ll focus on morphological traits that are rather consistent
right through that lineage. So what I’ll do is I’ll
go down from the cranium indicating what’s common
and how we understand whether that contributed to who we are, and what implications it has. When you look at the
cranium of Australopithecus, she has several cranial characters including a forward placed foramen magnum, indicating that this genus was bipedal. They had small brain size, small relative cranial height and breadth, prominent glabellar,
which is this region here, and relatively robust zygomatic bone, and also they had a jutting jaw. Those are just some of
the characteristics. They also had U-shaped dental arcades. The chimpanzees have almost
a rectangular dental arcade, and modern humans, we have
parabolic dental formula. When you look at the
brain, the general trend in human evolution is an
increase in cranial capacity and this trend become
much in the genus Homo. And usually it’s often associated
with consumption of meat. We know that brain size
increased more than threefold from Australopithecus
to our genus species. So you can see the Australopithecus here, they had very small brain size, and when you come to us it’s more than, it’s almost about three times what you see in the Australopithecines. One critical question in human evolution is the timing and mode of early human, early hominid brain evolution. As late as 2010, it was generally assumed that brain size increment
preceded brain reorganization. From 3.6 million years, that’s when we have the
Australopithecus prometheus, to two million years, which is represented by
Australopithecus sediba. Research indicates that Australopithecus’ cortical folding patterns
in the brain were, essentially, chimpanzee-like, Brain volumes are also
at least at the upper end of chimpanzee variation. However, Australopithecus sediba, which is represented here,
and also this is sediba, which was discovered in 2008, Australopithecus sediba
display human-like local protrusion in the inferior frontal area, which is that region
that’s highlighted here, and which the researchers,
led by Kris Carlson, they call this as an
implication of early stages of bolstering local neural
connectivity in area 45. In which, they argue,
is related to speech. Thus, the current consensus is that there is a gradual neural reorganization of the orbitofrontal region in the transition from
Australopithecus to Homo, but not gradual enlargement
before transition. So what does a increase
in brain size demand? An increase in brain
size demands an increase in energy intake and/or a reduction in energy allocation to other
energy demanding functions, for example, by adopting a more efficient bipedal locomotion, having a slower growth and production rate, and
having small smaller guts. All these factors have
been observed or inferred in the evolution from
Australopithecus to Homo. If you look at the
shoulders and the thorax, Australopithecus genus is characterized by a relatively elevated
shoulders and a conical shape in the upper thorax, which is, you can see the shoulders
here are elevated, This is Australopithecus
sediba, that’s modern humans, and that’s the chimpanzees, The shoulders are elevated,
so Australopithecus have this general shape, which
is similar to what we see in the chimpanzees. The high position shoulders
have been interpreted as indicative of upper limbs
that were habitually used in overhead postures in
the constant context of arboreal locomotion and
positional behaviors. That means they would have most of the time been
using their arms like this. That’s whether they were
climbing or using that for movements in the trees, A conical shaped torso,
as you can see on these, which is similar to what
you see in the chimpanzees. The humans have a barrel-shaped torso, is effective in evenly
distributing stress on the ribcage during hanging, but also these, a drawback to that because
it makes it difficult to swing arms when walking
upright or running. A barrel-shaped thorax,
as in modern humans, it was well adapted for
endurance walking and running. This is a depiction of
Australopithecus climbing, and you have to agree with me this has to be a very small
tree if they are holding on the branch and also on the ground. If you look at the forelimb, Australopithecus are
characterized by long arms with particularly light joint surfaces and a higher brachial index. This is great, the higher
brachial index is greater than the modern gorilla, but
lower than the chimpanzees, indicating retention of some
degree of arboreal competence. This would also imply an upper limb that was habitually used
in overhead postures in the context of arboreal locomotion and positional behaviors. When we look at the hand, Australopithecus possessed long, robust,
and curved fingers, with strong attachment
sites for flex muscles. The degree of curvature in
the shafts of the fingers is correlated with frequency
of arboreal behavior. Australopithecus phalanges
are intermediary curved between those of modern
humans and great apes, suggesting regular substantial
climbing and suspension. So the question is, did
Australopithecus make stone tools? And what we know is the
earliest stone tools dated to about 3.3 million years. They are called Lomekwian and
they predate the early members of the genus Homo by 800,000 years, and the genus Homo is thought
to have made the stone tools, so most likely Australopithecus
would have made stone tools. If you look at the spine and the legs, Australopithecus has five to
six broad lumbar vertebrae that articulated to form a
human-like lumbar curvature, effective for weight
transmission from the upper body to the pelvis, while also
permitting the hips and the trunk to swivel forward during walking. Australopithecus are characterized
by relatively short legs small femoral heads, small joint surfaces, and the small femoral necks are, however, longer and anteroposteriorly compressed than those of humans and
chimpanzees, and more higher angle. Shorter legs are less energy
efficient in bipedal walking, though they help in lowering
the center of gravity, hence, increasing stability and balance while walking on uneven substrate, Owen Lovejoy has suggested
that long femoral necks increased the mechanical
advantage of the hip muscle that stabilize the pelvis. When we look at also continuing
on the spine and leg, the distal tibia in
Australopithecus is characterized by anteroposteriorly expanded metaphysis, that’s this region here,
that has been interpreted as probable early bipedal adaptation that expanded volume of ankle for stress dissipation during walking. The foot of Australopithecus
has a large immobilized toe that’s in line with other
toes, as it’s evident in the 3.6 million year
old Laetoli footprints. And this alignment provides a strong push off during toe-off. While the pelvis of
Australopithecus is human-shaped, it’s extraordinary broad with a wide side-to-side birth canal, small sacral and coaxial
joints, long pubic rami. Kevin Hunt has argued that
a wider pelvis evolved to allow internal organs to
ride lower in the body cavity, thus, lowering the center of gravity, hence, increasing balance
while bipedal walking. Prior to discovery of
Australopithecus sediba, shown here, and this is modern humans, it was assumed that Homo-like
architecture of the pelvis was a result of giving birth
to large-brained babies. In 2005, Lovejoy argued
that the primary differences between the pelvis of
australopithecines and modern humans do not reflect changes
in locomotor adaptation, but instead are a complex and
elaborate anatomical response to birthing in response to increasing Pleistocene hominid cerebralization. However, the Homo-like pelvis
of Australopithecus sediba, coupled with a small adult brain, suggest that birthing
of large brain babies was not driving the
evolution of the pelvis at two million years. Looking at sexual dimorphism, Australopithecus exhibit a greater degree of sexual dimorphism than in
modern humans and chimpanzees. They possessed body weights
between 25 to 60 kilograms, with males at the high end
and females at the low, Females weighed somewhere
between 50 and 70% of male body weight. In modern humans females weigh about 85% of the male body weight. The degree of sexual
dimorphism has implications on social organization,
as well as mating systems. Primates species with
higher sexual dimorphism, are characterized by intense
male to male competition. As Larsen has observed, although chimpanzee adult males express aggressive behavior
toward one another, they tolerate each other, live in multi-male kin groups, and are cooperative, especially
in defending territory. Australopithecus social organization may similarly have been
characterized by multi-male, cooperating kin groups. So what are the
evolutionary relationships? Reconstructing hominid phylogenies
is extremely problematic and highly controversial. There is no consensus
among paleoanthropologists on how to go about it in the first place. Does one use age of the
fossil, geographical clarity, morphological traits? And if so, how many of those
morphological traits to use? Thus, there is no single
universally accepted phylogeny. My preference is not in drawing
lines connecting one species to another, but documenting
morphological traits and reasoning about the
implications of that in time and space. In conclusion, there are
three major conclusions that can be drawn from the studies we have about australopithecines. One, all australopithecines’
features considered together denote a small-bodied,
small-brained, robust-jawed, bipedal apes, that retained a
substantial arboreal component to their locomotor repertoire. Available morphological
evidence demonstrate that the evolutionary
transition from small-bodied and perhaps more arboreal adapted hominins such as Australopithecus africanus, to a larger bodied possibly
full-striding terrestrial biped such as Homo erectus
occurred in a mosaic fashion. In terms of stone tool making, we need to investigate the
relationship between posture, arm length, and their internal properties. and not just the morphological
traits of the hand to characterize a tool maker. And with that, thank you. (crowd applauds) (upbeat music)