Early Hominids 1

Australopithecines: the fossils and relationships; evolutionary pressures; bipedalism; intelligence.

Introduction

Today's lecture will follow on from the previous lecture and look at the last 5 million years of human evolution. In fact, I will concentrate on the Pliocene, and leave the last million years for later, since the human-like animal around then is very human-like indeed, and probably is better discussed by someone who doesn't claim to be a primatologist.

Lecture Outline

• Orientation
• The Sites
• The Fossils
• The Species
• How it all MIGHT fit together

Orientation

Australopithecines (Southern Apes)

Various species in Africa from 5 to 1 mya

Homo habilis (Handy man)

Africa: 2 to 1.5 mya

Homo erectus (Erect man)

Africa, East Asia, South East Asia: 1.8 mya to 100,000 ya

Homo sapiens

Archaic forms from 400,000 ya, modern forms from 200,000 ya. Africa, Asia, Europe.

Australopithecines

The Sites and Fossils

East Africa

East African rift valley system (1,200 miles long) associated with mountain building, faulting and vulcanism over last few million years. Earth movement mean sediments get exposed (Plio-Pleistocene 4 to 1 mya), and volcanic activity causes layers of volcanic ash (tuffs) which can be dated (potassium argon, or fission tracks) accurately.

Middle Awash

Now very important site called Aramis: Australopithecus ramidus, 4.4 mya. Though there is argument about whether this animal has enough derived features to be an australopithecine (need post-crania to be sure, and post-crania needs to be found in close context with cranial material to confirm species).

Laetoli

3.75 to 3.5 mya. Most famous for the Laetoli footprints: thousands of footprints of over 20 different species including hominins. One set of hominin tracks are of 2-3 individuals in a trail more than 25 m long - bipedal walking such as this is considered to be characteristic of hominins

Hadar

Very many fossils and artefacts. Fossils from 3.9 to 3 mya. Most famous is Lucy (Afar Locality (AL) 288-1), a 40% complete skeleton (one of only 2 hominin skeletons earlier than 100,000 ya). AL 333 is a group of over 13 individuals including 4 infants: a "catastrophic" assemblage perhaps.

Omo

Very thick continuous sequence (0.5 mile thick). 2.9 to 1 mya. Very rich fauna, so useful for biostratigraphic dating, but fossil hominins restricted to teeth and bone fragments.

East Turkana

Possibly the richest site. Approx. 1.8 mya, though there are some much older beds (3.3 mya). Complete skulls, jaws and postcrania.

West Turkana

West side of Lake Turcana. 2 very famous finds: an almost complete, 1.6 mya Homo erectus adolescent (see later) and the so called "black skull", a 2.4 mya robust australopithecine skull that is still causing problems with classification!

Olduvai Gorge

Mini Grand Canyon. 2 mya to present, providing an excellent sequence of fossils and artefacts, including the original robust australopithecine cranium.

South Africa

Unlike the East African deposits, the South African ones are all cave deposits - piles of mineralised sediment that has fallen into caves. They are not currently datable to any great accuracy, and the ages are usually inferred by looking at the faunal context of the fossil and comparing it to faunal remains from better dated sites. However, they have produced many fossils, including some good postcranial material (including pelvis: important for investigating bipedalism)

Taung

Limestone mine which produced the "Taung Child" in the 1920s. Before this, it was always thought that the earliest humans would be discovered in Europe, or perhaps the Far East. Consequently, it took quite a while before this discovery was accepted for what it was.

Sterkfontein, Kromdrai & Swartkrans

Another set of caves in SA. (Sterkfontein was another commercial lime works).

Makapansgat

Another cave...

The Species

A. ramidus

Not too much to say about this one. It appears to be more primitive than the others. There's some argument as to whether it is a hominin. Is discoverers would have us believe that it is the best human ancestor. Some good cranial material, but no post-crania. 4.4 mya. Possibly renamed as Ardipithecus ramidus due to the presence of certain ape-like features (thin enamel, narrow molars). However, it does appear to be upright due to the forward placement of the foramen magnum.

A. anamensis

Not too much to say about this one either. Found this year near Lake Turkana. About 3.9 to 4.2mya. Its discoverers think that it is the earliest human ancestor, and that A. ramidus is possibly an early chimp precursor. Jaws, teeth and a leg bone...

A. afarensis

Best fossils from Laetoli and Hadar, including Lucy, and in 1992, a reasonably complete cranium. Primitive teeth (large canines, parallel tooth rows); small brain (no bigger than chimp < 500 cm³); clearly bipedal (footprints, feet, pelvis, femur); rather ape-like wrist and pot-belly. Perhaps as much as 4.5 mya, but only certain after 4 mya.

Possible extreme sexual dimorphism, or maybe 2 contemporaneous species.

A. robustus, A. aethiopicus, A. boisei (robust australopithecines)

2.5 mya. Earliest is WT-17000 (West Turkana) A. aethiopicus. Small brained (410 cm³), teeth diverge at rear (primitive traits), but also has derived, robust australopithecine traits: broad face; large palate; large back teeth. Intermediate between A. afarensis and the other robusts? 2 mya A. boisei from East Africa - "nutcracker man" - very robust; huge back teeth; very broad face (Zinjanthropus). Also A. robustus from South Africa - similar date. Possibly a tool user. Have tools from South Africa, but there was a sympatric, contemporaneous Homo habilis which may have made the tools.

Note: some authors put these animals into a separate genus Paranthropus.

A. africanus (gracile australopithecines)

South African only. Although not much difference in overall body size compared to robusts, has much smaller face. Has smaller molars, but larger canines and incisors than the robusts, though still larger than modern humans. Thought to be linked to a very different diet.

Tool Use

As I mentioned in yesterday's lecture, tool use is considered to be a sign of higher cognitive abilities. It was once thought to be one of the features that set humans apart from other animals, and indeed, if one looks at the range and sophistication of the tools that humans use, then this is indeed true. However, tool use has been seen in a number of primate species, including early hominins, and the study of these tools provides important information concerning the evolution of the human tool using abilities.

This lecture is about tool use in NHP and tool use in early hominins up to early humans about 100,000 ya.

Introduction

Tools can loosely be defined as any object manipulated by an animal in order to perform a specific task. It might further be defined by suggesting that the task has some benefit to the animal, and that the task is made easier by the use of the tool, though neither of these criteria is necessary. It is unclear whether novel uses of parts of the animal's own body constitute tool use: for example, orang-utans have been observed to spit fruit onto their fur and lick it off, presumably to help remove some of the seeds.

Tools can thus be very simple - a bunch of leaves used as a sponge to carry water, for example, of a stick to help scratch the animal's back. This sort of tool which requires no alteration to be functional, is sometimes described as a "naturefact".

In this context, an "artefact" is a tool that has been crafted: altered in some way to make it more suitable for the job in hand. For example, chimps have been know to chew their termite fishing sticks so that they fit better into the holes in the termite mounds. A chewed stick is now an artefact. Oswald has produced a table that broadly categorizes artefacts in terms of increasing complexity:

1. Reduction: reduce mass of functional form (e.g. our chewed stick, or a flaked flint.
2. Conjunction: combine 2 or more units to make tool (e.g. a flint headed spear, or a hafted axe)
3. Replication: conjunction but with 2 or more similar units required (e.g. a double pronged fishing spear)
4. Linkage: physically distinct forms in combination (e.g. a bow and arrow)

In the context of this lecture, I shall cover categories 1 and 2, since 3 and for are almost certainly the sphere of true humans.

NHP Tool Use

Non-human primate tool use seems to fit into 2 categories. Some NWMs in the wild, and a number of OWMs in captivity have been seen to use tools. In addition, all the great apes seem to be able to use tools, though they've not all been observed to do so in the wild. However, there seems to be a cognitive difference in how they perceive their tools.

Capuchin monkeys

Capuchin monkeys (e.g. Cebus apella) are observed to use stones to crack nuts in the wild. This behaviour has been much studied in captivity with some interesting observations:

1. Not all animals seem capable of learning to use tools
2. They don't seem to "understand" their tools (e.g. banging the ground next to the nut)
3. Other members of the group are able to learn to use tools by observation
4. In captivity, they will use other tools to perform particular tasks (e.g. honey dipping with straw)

It has been suggested that capuchin tool use is not a result of cognitive ability (though capuchins do have bigger brains than would be expected for such small monkeys), but are an almost accidental feature of their destructive foraging methods. However, in captivity, they have been observed to produce conjunction tools: sticking 2 pieces of straw together to make a longer probe to reach rewards farther away from the cage than they could reach with a single straw, which may indicate quite a large degree of sophistication.

There is certainly a very large difference in their enthusiasm for tool use.

Great Ape

In general, although all the great apes are competent tool users in captivity, only common chimpanzees have been observed as regular tool users in the wild. This may, of course be due to the fact that chimps have been much more widely studied, and for longer periods than the other great apes.

Here is a list of the observed use of tools among chimps (#CMC180). As you can see, there is a very great difference in the observed tool usage at the different sites. Tool use would therefore appear to be a very cultural phenomena - use is restricted to, and passed on within a limited population.

In captivity, all the great apes have used a wide variety of tools that have not been seen in the wild: from branches used as pitons to aid escape to flaked stone tools to cut ropes tying shut boxes containing food. (#CMC 221) It might be suggested that these animals have an untapped tool making and using ability that is simply not required in their current environment. This begs the question, "Why?" Was the common ancestor of the great apes a much more avid tool user with its environment encouraging tool use at any opportunity? Or is tool using ability just a largely latent feature of having a large brain (for whatever ultimate reason great apes have large brains, be it foraging or social complexity). We will probably never know the answer.

Early Hominins

Although early hominins undoubtedly used a number of different tools in much the same way as chimpanzees, the only ones we have any evidence for are the stone tools. Chimps, as mentioned, do use stone tools, and even have preferred hammer and anvil stones that clearly show signs of wear, and this might be the very first stone tools that we would expect to find - although they might not be that easy to spot.

What is much easier to spot are the tools made of siliceous rocks. These rocks (of which flint is the best known example) are fairly homogeneous and without any obvious crystal structure which fracture in a "conchoidal" (shell-like) fashion when hit. This pattern of fracturing is usually relatively easy to spot, and produces very characteristic flakes with what are termed as "shock ripples" and a "bulb of percussion". This latter is a rounded bulge near the point of impact of the hammer used to create the flake.

H. Habilis (Oldowan)

The very earliest stone tools have been associated with Homo habilis (though they might be associate with robust australopithecines) and are termed "Oldowan" after Olduvai gorge where they were first found. They date back about 2.6 mya and consist of crudely flaked "chopper cores" (#NSUF 33). Interestingly, the way that the initial chunky flake was produced was probably also the technique that has been observed in pygmy chimps: hurling the rock at a stone anvil (anvil technique) (#NSUF 31). For those of you who want to try this at home, it is not a recommended technique...

A safer way of producing these chunky flakes is by direct percussion using a suitable hammer stone (a granite pebble for example). This same hammer can then be used to touch up the initial flake to produce a better cutting edge. (#CGPM 108) The tools produced are relatively crude and quite varied.

H. Erectus (Acheulean)

The next improvement in stone tools is associated with Homo erectus and is called the Acheulean (named after a 300,000 ya set of stone tools found at ST. Acheul in France). The classic example of an Acheulean stone tool is the hand axe (#CGPM 126). These date back about 1 mya. Given the limited overlap between the habilines and the erectus people, it seem likely that erectus must have started producing Oldowan style tools first, and then gradually moved over to Acheulean styles. In a similar way, early H. sapiens must have produced Acheulean style tools before moving onto the more advanced forms of the Mousterian.

If animal classification caused you sleepless night, then stone tool classification is even worse! Stone tools don't really have homologous features as such, and almost certainly form a continuum from simple to more complex.

Acheulean technologies are the first examples of "bifaces". These are stone tools that are flaked on both sides (#CGPM 127). This requires rather more skill, and a great many more strikes per tool. The tools produced certainly look better, and the fact that they are rather thinner than monofacial chopper would indicate that they were superior for cutting meat etc.

We also have evidence of wooden and bone tools associated with H. erectus all from Ambrona or Torralba in Spain.

In addition there appears to be a certain style associated with these and subsequent tools. Tool appearance rather than just functionality seems to have some importance. This may be an indication of some sort of higher level cognition.

Advanced Flint Tools

The next stage onward: referred to as Mousterian (Le Moustier in France) seems to be a set of improvements designed to maximise the number of tools produce from a piece of flint. Tools are produced from the flakes removed from the cores, not the cores themselves. This improvement in efficiency can be seen from the following diagram (#CGPM 145).

The first of these techniques is referred to as "blade core technology" (#NSUF 52). Where multiple long blades are struck from the core. This (and other core technologies) require more accurate striking of the core, and modern flint knappers often use indirect percussion (hammer hitting a chisel made of wood, bone or antler) to improve precision.

The second technique is "flake core" technology (Levallois flakes) (#NSUF 58) which produces rather regular, flattened flakes rather than blades. The key feature of these flakes is that, made properly, both sides are convex so that the flake is both strong and sharp (#NSUF 59)

Summary

That is a whistle stop tour though animal tool use and lithic technology. The overlap between chimp tool use and that of early hominins seems very striking, and would certainly be unexpected to most palaeoanthropologists even 10 years ago.

It is clear that early hominins had a cultural progression of tool use that was not specifically linked to one species or another (though some may claim this).

Bibliography

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  TI: NEW 4-MILLION-YEAR-OLD HOMINID SPECIES FROM KANAPOI AND ALLIA BAY,
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  AU: LEAKEY_MG, FEIBEL_CS, MCDOUGALL_I, WALKER_A
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  TI: AUSTRALOPITHECUS-RAMIDUS, A NEW SPECIES OF EARLY HOMINID FROM ARAMIS,
      ETHIOPIA (VOL 371, PG 306, 1994)
  AU: WHITE_TD, SUWA_G, ASFAW_B
  JN: NATURE, 1995, Vol.375, No.6526, p.88

  TI: BONES OF CONTENTION
  AU: LEWIN_R
  JN: NEW SCIENTIST, 1995, Vol.148, No.2002, pp.14-15

  TI: STERKFONTEIN-MEMBER-2 FOOT BONES OF THE OLDEST SOUTH-AFRICAN HOMINID
  AU: CLARKE_RJ, TOBIAS_PV
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Other

Conroy, G. C., 1990. Primate Evolution, Norton, London.

Bahain, J. J., Grimaud-Hervé, D., Serre F., 1993. Histoire D'Ancêtres, la grande aventure de la préhistoire, Musées/Homme, Paris.

Lord, J. W., 1993. The Nature and Sunsequent Uses of Flint, Volume 1, The Basics of Lithic Technology.