The emergence of Homo sapienscame at the end of a long, slow process of change from a quadrupedal, arboreal existence to a bipedal, grassland lifestyle (Haviland, 1996). These changes occurred gradually over a period of 40–50 million years as a chain of species emerged, evolved and became
Table 6.1. Diversity of plant structures eaten by Homo sapiens.
Plant part Example
Root Beet, radish and carrot
Above-ground stem Sugar cane Underground stems
Tuber Potato, yam and cassava
Corm Taro
Bulb Onion
Leaf Cabbage, lettuce and tea
Inflorescence Cauliflower and broccoli Fruit
Multiple Pineapple, fig and breadfruit Aggregate Raspberry and strawberry
Pome Apple and pear
Drupe Peach, olive, coconut and mango Hesperidium Orange and lemon
Pepo Cucumber, water melon and cantaloup
Nut Walnut and hazelnut
Grain Wheat, rice, maize and barley Achene Sunflower and safflower
Legume Bean, pea, groundnut and soybean
Table 6.2. Selected food families.
Family Crop
Dicotyledoneae
Anacardiaceae Mangifera – mango Camelliaceae Camellia – tea Caricaceae Carica – pawpaw Chenopodiaceae Beta– sugar beet Compositae Carthamus– safflower
Helianthus– sunflower, Jerusalem artichoke Lactuca– lettuce
Convolvulaceae Ipomoea– sweet potato
Cruciferae Brassica– kale, cabbage, turnip, rape Cucurbitaceae Cucumis– cucumber, melons
Cucurbita– squash, gourds Euphorbiaceae Manihot– cassava Lauraceae Persea– avocado Leguminosae Arachis– groundnut
Cajanus– pigeon-pea Cicer– chickpea Glycine– soybean Lens – lentil Phaseolus– beans Pisum – peas Vicia– field bean Vigna– cowpeas Moraceae Artocarpus– breadfruit
Ficus– fig Oleaceae Olea– olive
Phoenix– date palm Pedaliaceae Sesamum– sesame Rosaceae Fragaria– strawberry
Malus – apples
Prunus– cherry, peach, almond Rubus– raspberries, blackberries Rubiaceae Coffee– coffee
Rutaceae Citrus– orange, lime Solanaceae Capsicum– peppers Lycopersicon– tomato Solanum– aubergine, potato Vitaceae Vitus, Muscadinia– grapes Monocotyledoneae
Araceae Colocacia– taro Bromeliaceae Ananas– pineapple Dioscoreaceae Dioscorea– yams
Continued
extinct. Our ancestry can be traced back to the earliest tree-dwelling pri- mates that inhabited the forests over 50 million years ago. Monkeys and apes diverged into separate lineages 20–30 million years ago, and the first hominids evolved from apes 15 million years ago (Fig. 6.1).
Several traits changed dramatically during the evolution ofH. sapiensto make us what we are: (i) faces became flatter and craniums increased in size; (ii) teeth became more generalized, as incisors and canines became reduced and molars became more massive and flat; (iii) cheek teeth became less separated and the jaw more interlocking; (iv) individuals gained the abil- ity to swing in limbs or brachiate, as forearms became shorter than hind limbs and the size of the thumb became reduced so that the hand could function as a hook; and (v) upright or bipedal motion evolved, as a lumbar curve developed in the vertebral column, the pelvis became larger and the head and hip became repositioned. These changes were initially associated with increased diversification in a forest environment, but ultimately led to the effective exploitation of the surrounding grasslands.
The initial emergence of hominids was probably stimulated by the climatic changes associated with the Miocene 15 million years ago. The climate became much drier and tropical forests began to break up into mosaics of forest surrounded by open bush country. The ape Sivapithecusevolved at the forest margins with the ability to occasionally stand upright, carry food, scan the countryside for predators, perhaps throw things and scamper back to the safety of trees. Doubtless, this creature was in stiff competition with other mam- mals for food, and had to keep a sharp eye out for predators.
Our first fully upright ancestor, Aripithecus ramidus, appeared between 4.4 and 3.9 million years ago, but is represented by only a few fragmented
Table 6.2. Continued.
Family Crop
Monocotyledoneae(Continued) Gramineae Avena– oats
Eleusine– finger millet Hordeum– barley Oryza– rice
Pennisetum– pearl millet Saccharum– sugar cane Secale– rye
Sorghum– sorghum Triticum– wheat Zea– maize Liliaceae Allium– onion
Musa– bananas
Palmae Cocos– coconut
Elaeis– oil-palm
skeletons from Ethiopia and Kenya (Tattersall, 1998). The first widespread bipedal species to appear belonged to the genus Australopithecus, which emerged about 4 million years ago. Convincing fossil evidence of this genus has been found at several locations in Africa, including a perfect set of foot- prints found by Mary Leakey in Tanzania (Johanson and White, 1979).
These protohumans were omnivores, with small canines and heavily enam- elled molars that could process abrasive seeds. It is not known whether they just scavenged or hunted for food, but among their remains are high num- bers of limb bones from hoofed animals, suggesting meat was brought back from butchering sites. It may have taken primitive cutting tools to do this, and the bones themselves may have been those tools.
Geological Epochs Pleistocene Pliocene
Miocene
Oligocene Eocene
Old World Monkeys (living genera)
Gibbons Great Apes Orang-utan
African
Apes Humans Homo
Million Years Ago
40 35 30 25 20 15 10 5 0
Earliest Arthropoids
Propliopithecus Aegyptopithecus Apidium
Dryopithecus Sivapithecus
‘Ramspithecus
’(?)
Oreopithecus Pliopithecus
Gigantopithecus
Aus
tralopithecus
Parapithecus
Fig. 6.1.Evolutionary relationships of apes and humans (used with permission from W.A. Haviland, © 1996, Human Evolution and Prehistory, Reinhart and Winston, New York).
The most famous member of this genus is ‘Lucy’, discovered by D.C.
Johanson in northern Ethiopia (Johanson and Eday, 1981). Almost 40% of the skeleton of this young women remains, along with fossils of dozens of other members of her species, Australopithecus afarensis. No one really knows why the remains of so many individuals ended up together, but it has been speculated that a group of them may have been killed together by a flash flood or a particularly virulent disease. They could also have been the pile of bones left behind by a predator.
While the story is still unfolding, numerous species of Australopithecus appear to have roamed the earth at one time or the other, some even as con- temporaries (Johanson and White, 1979; Lasker and Tyzzer, 1982; Leakey and Lewin, 1992). There were small and slightly built ‘gracile’ forms that weighed as little as 60 pounds (A. afarensis and Australopithecus africanus), and more ‘robust’ forms (Australopithecus robustusand Australopithecus boi- sei) that approached 150 pounds. The relationships between species of these two groups and later Homo are very much in dispute, but most scientists agree that Lucy’s species, A. afarensis, is in the direct ancestry of our genus, Homo (Leakey and Lewin, 1992; Fig. 6.2). The robust forms represent deriv- atives that evolved on one or more separate branches from ours. One won-
Homo sapiens
Homo erectus
Homo habilis Australopithecus
afarensis 0
1
2
3
Time (millions of years before present)
Fig. 6.2. One of the plausible continua of human evolution. Many proposed intermediate forms are not included (see text).
ders how much contact these various species had and if competition between them actually stimulated our own emergence.
Even though Australopithecus species underwent considerable mor- phological change during their 3 million years on earth, their cultural devel- opment remained stagnant. In many ways, these ‘southern apes’ were no better equipped to cope with the vagaries of nature than other contempo- rary organisms. The invention of agriculture was far from their capabilities.
They existed for millions of years, so it is unfair to call them an evolutionary failure, but real cultural advancement awaited the appearance of their brighter cousins, Homo, about 2–2.5 million years ago. These early Homo showed a dramatic increase in cranial capacity from the 380–500 cm3 of Australopithecus to 600–775 cm3, and, over the next 1 million years of Homo’s evolution, average brain size increased another 900 cm3 (Haviland, 1996).
While it has long been popular to talk about the ‘missing links’ in hominid evolution, an almost continual record of gradual morphological change is now available, which represents changes not only in brain size, but also in skull shape, dental traits, forearm length and pelvis size.
Richard Leakey and R. Lewin suggest in their book Origins Reconsidered that we have, in Africa alone, ‘fossilized fragments of about a thousand human individuals from the early part of our evolution’. Fossils have been found with almost every conceivable combination of human and ape char- acteristics. It is becoming increasingly difficult to determine which fossil remains constitute real species change and which represent the simple extremes of species variability.
The earliest fossils that are commonly attributed to our genus have been found in East Africa, eastern Ethiopia and South Africa, and represent a diverse group (Leakey, 1971; Leakey and Lewin, 1992; Haviland, 1996).
Louis Leakey named one of these creatures Homo habilis, or ‘handy person’
(Fig. 6.2). Other early collections of bones have been referred to as Homo ergaster and Homo rudolfensis. Archaic Homo were the earliest hominid toolmakers, producing what are called ‘Oldowan’ tools by battering rocks together to remove a few flakes (Washburn and Moore, 1980; Fig. 6.3).
These primitive tools were used to perform a wide array of daily tasks such as cutting, chopping, scraping and perhaps defence.
The early Homo were hunters of small and medium-sized animals including rodents, snakes, antelopes and pigs. They probably supplemented their diets by scavenging the left-overs of larger animals and gathering plant material, but there is still no evidence that they practised agriculture. They lived together in base camps of temporary shelters, evidenced by semicircu- lar concentrations of tools and marrow-bearing bones and circles of stones that may have been used to support branches. These early people are unlikely to have had well developed speech, but they had clearly begun down the human path, as they made tools, shared food and returned to a base camp.