The Earliest Members of the Neanderthal Lineage

Another group of mainly European specimens, which some believe represent the basal stock from which the Neanderthal ultimately evolved, have been allocated to a species H. steinheimensis; for the moment we (partly following Howell, 1998) will use this name. This species is best represented by its type specimen, the Steinheim skull near Stuttgart in Germany (Figure 7.6), the Sima de los Huesos specimens from Atapuerca in northern Spain, the Swanscombe cranium from England, and the Narmada cranium from India, most of them considered to date between 300,000 and 230,000 years ago (Howell, 1998; Schwartz and Tattersall, 2002; Klein, 1999; Cameron et al, in press), although Stringer and Hublin have recently made a strong case that Swanscombe is actually much older, around 400,000 years old, as may be Atapuerca. This species is contemporary in time and space with the later surviving African and southern European demes of H. heidelbergensis. As we will see in the next chapter, the molecular evidence from the Neanderthals suggests that H. steinheimensis is close to the probable time of divergence of the Neanderthal lineage from those that ultimately evolved into the earliest modern humans — around 500,000-700,000 years ago.

In its morphology, H. steinheimensis clearly displays incipient Neanderthal features, including, to varying degrees, the configuration of the supraorbital tori, the large size of the nasal opening, the medial projection from the side walls of the nasal cavity, developed occipital torus and suprainiac depression, and a long cranium with a slightly more elevated frontal bone

Depression Suprainica

(associated with neuro-orbital convergence). While some of these features may be seen in specimens of H. heidelbergensis (at least in their incipient form), it is this combination that is important; it indicates that H. stein-heimensis stands at the root of the Neanderthal lineage. Indeed, proposed similarities between some H. heidelbergensis specimens (especially Petralona) and the later "classic Neanderthals" can at least be partly explained by their common expansion of their frontal and maxillary sinus systems; the phylogenetic significance of this remains obscure, and it is seen in some African specimens too (such as Bodo). The shared presence of these features in H. heidelbergensis, H. steinheimensis and H. neanderthalensis may represent either a functional and/or developmental convergence or the persistence of a primitive feature that was variably developed in H. heidel-bergensis but became emphasized in H. steinheimensis and even more so in H. neanderthalensis. The Atapuerca evidence shows for the first time the robust postcrania that are indicative of an adaptation to a cold climate.

In some aspects of their cranial morphology, however, H. steinheimen-sis is still primitive, and they do not display the Neanderthal "en bombe" shape (Hublin, 1998). Hublin (1998) and Stringer (1998) argued that many of the Neanderthal features probably began as uncommon polymorphic variants, which gradually increased in frequency through time as a result of selection pressures. This ultimately resulted in the "classic" Neanderthal morphological condition, but they are already incipiently developed in H. steinheimensis.

The complete but distorted Steinheim cranium was found in 1933 within a gravel pit. The estimated cranial capacity is 1100 cc (Aiello & Dean, 1990), and the specimen is currently dated to around 225,000 years ago (see Schwartz & Tattersall, 2002). Its phylogenetic relationship to H. erectus, H. neanderthalensis, and H. sapiens has long been debated, though the recognition that it has a number of derived Neanderthal-like features suggests that it represents a likely population from which the Neanderthal lineage evolved. Of particular significance is the medial projection within the lateral nasal aperture, which Schwartz and Tattersall (2002) and Tattersall and Schwartz (2000) consider to be a derived feature of the Neanderthal lineage. It also has a number of other incipient Neanderthal-like features, including its similarity in supraorbital form, a midface that is relatively prognathic (forward projection of the nasal aperture), and an occipital torus and suprainiac depression, though only weakly developed, as well as a weakly developed mastoid process (Stringer & Gamble, 1993; Wolpoff, 1999).

The Sima de los Huesos (Atapuerca) fossils have a cranial capacity ranging from 1125 to 1390 cc (Stringer, 2000a) and are currently dated to 300,000 or more years ago (Arsuaga et al., 1997; Schwartz & Tattersall, 2002). In terms of their projected brain mass relative to body mass, they are around 3.1-3.8 times larger than expected for a mammal of its weight. As we will see in the next chapter, according to body weight, Neanderthals have a brain that is around 4.8 times greater than predicted, while H. sapiens have a brain weight 5.3 times greater than predicted (Arsuaga, 2002). They show a number of derived Neanderthal features, including the smoothly rolled, double-arched supraorbital torus, large and prognathic nasal aperture, and the horizontal suture over the mastoid region, as well as increased development of the frontal and maxillary sinus system (Tattersall & Schwartz, 2000). The presence and development of the medial internal nasal margin is variable in the Atapuerca specimens (Figure 7.7). For example, this feature is absent in crania 5 and 6 while being slightly developed in AT-638, AT-772, and AT-1665 and more markedly developed in AT-1100, AT-1111, AT-1197, AT-1198, and AT-1666 (Arsuaga et al., 1997). In addition, Arsuaga (2002) has estimated, according to correlations of pelvic breadth and overall height (determined from preserved femora), that the body weight of these hominins would have been even greater than the estimates for the later Neanderthals;

Figure 7.7 ► Homo "steinheimensis" specimen V from Atapuerca: Sima de los Huesos, Spain.

Homo Bergensis Skull Diagram

Figure 7.7 ► Homo "steinheimensis" specimen V from Atapuerca: Sima de los Huesos, Spain.

that is, some individual Sima de los Huesos hominins would have weighed between 198 and perhaps 220 pounds! The combination of these and a number of other features has suggested to Tattersall and Schwartz (2000) that the Atapuerca specimens may in the future need to be allocated to their own species. But we cannot see any real evidence for this, and we accept them as representing H. steinheimensis, a species whose validity is itself questionable (see later).

The original Swanscombe occipital was found in 1935, the left parietal was found in 1936, and the right parietal was not found until 1955. But all three specimens can be fitted together and clearly belong to the same individual. Swanscombe has traditionally been viewed as sharing a close relationship with Steinheim (Morant, 1938; Howell, 1960; Stringer et al., 1984; Wolpoff, 1996). Its estimated cranial capacity is 1325 cc (Aiello & Dean, 1990). The suggestion by Santa Luca (1978) and more recently by Stringer and Gamble (1993) and Stringer (2000a) that Swanscombe represents a likely forerunner to the Neanderthals has been endorsed by Schwartz and Tattersall (2002), who have allocated it to H. steinheimensis. This allocation is further corroborated by its gracile and double-arched occipital torus, the presence immediately above the torus of a suprainiac fossa, and, finally, the suggestion of a developed juxtamastoid eminence at the occipital margins (Stringer, 2000a). If the analysis of Stringer and Hublin (1999) is cogent and it is 400,000 years old, then it is clearly the oldest example of its species.

Earlier we asked whether there is value in recognizing a species Homo heidelbergensis, and we indicated that indeed there is. The question of whether H. steinheimensis "exists," in any meaningful sense, is more equivocal. Without a doubt, we are dealing with the stem group of the Neanderthals: All the basic Neanderthal derived traits are present, but in an incipient form. The specimens we have been describing occupy a position intermediate between H. heidelbergensis, which has none of these derived states, and true (classic) Neanderthals, in which these states are fully expressed. Under Hublin's "accretion model," the specimens would be placed along an unbroken continuum; in the Composite Species concept (Kornet, 1993), they would be classified as Homo neanderthalensis. The latter seems the more sensible option: What we have been describing are early, primitive Neanderthals.

The "Steinheim group," as we will call them, are known mostly from Europe, but there is a surprising exception. The Narmada cranium from central India has an estimated cranial capacity of 1290 cc (Kennedy et al., 1991)

and is, according to Cameron et al. (in press), 230,000 years old. According to Cameron et al. (in press), Narmada shares a numbers of unique features with the Steinheim skull and to a lesser degree with the specimens from Sima de los Huesos. These similarities include a long but more elevated cranium associated with neuro-orbital convergence, similar supraorbital torus development and form, and a similar degree of postorbital constriction. Groves (1989a) saw it as an Indian representative of Homo heidelbergensis, relict of the eastward extension of this species that ended up in China; but the presence of definite (proto-) Neanderthal features places that hypothesis in doubt. Indeed, a recent parsimony analysis by Cameron et al. (in press) confirms the sister-group relationship between the Narmada and Steinheim specimens. This indicates that the Narmada hominin represents a member of the "Steinheim group" that spread its range to the subcontinent around 250,000 years ago (if not considerably earlier). It may be that the Indian population died out, or maybe it, too, extended its range into China because, as we will show later on, there is quite a definite Classic Neanderthal in the late middle Pleistocene in the far south of China.

While we have no material culture associated with the Sima de los Huesos or Steinheim hominins, the artifacts associated with the Swanscombe cranium represent a classic Mode 2 technology (Acheulean), most similar to that associated with the Boxgrove hominin (Stringer & Gamble, 1993; Gamble, 1999). The near-contemporary Narmada cranium is also associated with an industry consisting of hand axes and numerous cleavers (M.A. de Lumley & Sonakia, 1985; Cameron et al., in press). Thus the material culture of the "Steinheim group," as defined by Swanscombe and Narmada, is associated with a primitive Mode 2 technology.

We have seen that the speciation event that marked the emergence of early Homo in Africa is associated with the adaptation of increased meat eating and with corresponding shifts in behavior that are required to obtain the resources from the sort of walking larder that runs away from you — increased territorial range. Perhaps the development of the biface industry (Mode 2 technology) helped to obtain and process these resources. This industry is maintained in Africa for over a million years. It begins with later stages of H. ergaster in Africa and persists into H. heidelbergensis in both Africa and Europe. The emergent earliest hominins in Europe, whether H. ergaster (H. georgicus?), H. erectus, or H. antecessor, however, still used a pebble tool industry (Mode 1 technology), and it is not until the arrival of H. heidelbergensis in Europe around 500,000 years ago that a Mode 2 technology appears (Foley & Lahr, 1997). The use of a

Mode 1 toolkit by H. erectus has already been discussed. Given the likely westward migration of H. erectus into Europe, the late survival of Mode 1 can be explained (see also partly Tattersall & Schwartz, 2000). The maintenance of a Mode 1 technology by H. antecessor suggests very strongly an older hominin penetration into Europe from an ancestral group that did not have access to a Mode 2 technology. If we are to believe in a one-to-one association of species and technology mode, then we have argued ourselves into the position that H. antecessor was not ancestral to later European populations, but was replaced by H. heidelbergensis coming in from Africa. If such associations do not exist, then H. antecessor may still have been ancestral to H. heidelbergensis, and Mode 2 spread into Europe from Africa without new gene flow.

Mode 2 lasted an amazingly long time without appreciable change. Several people have noticed that hand axes are skillfully made and aesthetically pleasing. Miller (2000) has argued that they were a product of sexual selection — the production of the most elegant examples was an indicator of the producers' intellectual, hence sexual, fitness.

Microscopic analysis of the lithic artefacts from Hoxne in Suffolk (around 400,000 years old) indicate that they were used to process a number of different materials. These all-purpose tools were used to cut meat and work hides, bone, and wood. They were also used to chop up vegetable matter (see Gamble, 1999; Jordan, 1999).

These later middle Pleistocene hominins were not restricted to only using a lithic technology, but clearly also used wood, as evidenced by the Clacton spear found in Essex, which dates to around 450,000 years ago. Whether it is really a spear or a digging stick is still being debated, but either way it is significant because it reminds us that such material, not usually preserved in the archaeological record, should not be discounted — absence of evidence is not evidence of absence. Indeed, additional (presumed) throwing spears that are 2.3 meters in length have been discovered from Schöningen in Germany. There is also evidence of toolkits having been made of stone, including flakes struck on anvils from elephant and rhino long bones, and there is even a bone biface from Castel di Guido in Italy dating to around 450,000 years ago (Gamble, 1999).

While the difference in morphology and between the more "primitive" technology used by the earliest Europeans and the more "advanced" technologies used in Africa can at least be explained by patterns of migration out of (and into) Africa, the later emergence of the "Steinheim group" proto-Neanderthals cannot be associated with any technological innovations: They appear to have used a Mode 2 technology just like H. heidelbergensis, and there is no evidence that there was anything different about their behavioral repertoire. Climate change and its associated habitat instability may be solely responsible for the speciation event in the middle Pleistocene of Europe: The more they specialized anatomically, the more they were able to cope with the climatic rigors of ice age Europe and the more of periglacial Europe they could inhabit.

Ever more severe climatic oscillations were starting to dominate Europe, if not Africa. Populations of H. heidelbergensis persisted in warmer southern Europe (i.e., Petralona), while contemporary demes of the "Steinheim group" lived in the northern latitudes, within extremely cold conditions. As cold climates spread south, these proto-Neanderthals spread with them: They are found with cold-climate fauna at Atapuerca in northern Spain; when climates ameliorated, H. heidelbergensis in its turn was capable of spreading to northern latitudes, such as England (Boxgrove). This reminds us that the distribution of these two species was dictated more by climatic and associated ecological factors than by a simple north/south geographical divide; throughout human evolution our forebears have been, like any other animal, subject to ecological constraints. Our present degree of cultural buffering from environmental extremes is a very recent phenomenon indeed and is still, in fact, far from complete. From time to time, extreme events, such as the prolonged droughts that afflict Australia and West Africa every few decades, or the recurrent monsoon failures of India, or the acid rains and soil salinity that result from botched attempts to further shelter human populations from environmental vicissitudes, remind us how very incomplete is this buffering, even today. Animals we were in the middle Pleistocene, and animals we remain.

Because the African and European H. heidelbergensis are similar in all respects, as far as our analysis goes, we should be wary of ascribing large sinus systems and so on to "adaptation to cold conditions." There certainly was no requirement for contemporary African demes to adapt to such conditions. Yet this morphological complex proved an excellent exaptation for those populations that were at the fringes and eventually occupied the northern latitudes of ice age Europe. These northern populations became increasingly isolated physically, culturally, and genetically, eventually giving rise to the proto-Neanderthals. The southern demes, however, continued to exist in the relatively warmer conditions of southern Europe and the temperate to tropical conditions of Africa.

There is some support for such a scheme in the geological and paleon-tological record, which provides a climatic history of Europe during this time (Figure 7.8). For example, while glacial conditions had started to occur during the Plio-/Pleistocene transition (if not before), a major change occurred around 750,000 years ago, when the glacial conditions became longer in duration, while the interglacials were significantly reduced, and overall climatic fluctuations became more marked. This is associated with the Brunhes Magnetic Polarity switch to normal. From the

H. sapiens

H. erectus

H. neanderthalensis

500,000

1 Ma

H. sapiens

H. neanderthalensis

H. ergaster

H. georgicus

2 Ma

H. georgicus

H. habilis

H. habilis

Figure 7.8 ► Implied phylogeny of the species we recognize within the genus Homo (see text for details).

Plio-/Pleistocene transition, around 1.8 million years ago, to around 900,000 years ago, a full glacial-interglacial cycle occurred every 40,000 years; between 900,000 and 450,000 years ago, however, it had increased to a 70,000-year cycle; and from 450,000 years ago to the present the cycle is around 100,000 years long (Stringer & Gamble, 1993). One of the longest and coldest patterns of glaciation occurred between 301,000 and 242,000 years ago (Stringer & Gamble, 1993; Gamble, 1999), just at about the time that the "Steinheim group" made its appearance in northern and central Europe and, presumably during the height of the cold phase, spread at least as far as central India. This was quickly followed by another, even colder period between 186,000 and 127,000 years ago (Stringer & Gamble, 1993; Gamble, 1999), corresponding with the emergence of the "classic Neanderthals."

Associated with these unstable cycles of glaciation and interglacial periods in Europe were corresponding fluctuations in the distribution of fauna and flora throughout the continent. During periods of glaciation, most vegetation types became extinct in northern and central Europe, and it is only in southern Europe that continuous pollen sequences exist (Tzedakis & Bennett, 1995; Gamble, 1999; Agusti & Anton, 2002). This was also the case for the many animal groups that were reliant on these food types, which during glacial times must have moved into the refuge of southern Europe. When the interglacial returned, the cold-adapted animal species like mammoth and reindeer moved back to the most northerly regions, as the forests and forest-dependent animals reoccupied central and parts of northern Europe (Geist, 1978; Guthrie, 1984; Gamble, 1986, 1999). It could be that early demes of the "Steinheim group" became more reliant on the cold-adapted faunal groups and followed their migration into the northern regions during interglacial periods, while the contemporary and more southern populations of H. heidelbergensis were more reliant on the forest-adapted mammal groups and vegetative material to the south. As discussed in the previous chapter, H. heidelbergensis made it into China, for a brief time at least, as illustrated by the specimens from Dali and Jinniushan. Thus H. heidelbergensis may have remained a warm-climate species, and as such, more of a generalist in dietary requirements; while the "Steinheim group" adapted more and more to an ice-bound Europe and by necessity became less reliant on a vegetable diet, with more and more meat consumption as it became increasingly adapted to its local conditions, and more and more specialized. What this specialization led to is the subject of the next chapter.

Interlude 4 The Geography of Humanity

Where do you live, Australian reader? Sydney, Melbourne, Canberra? Take a trip to Perth, and look around you. The animals are different, aren't they? Not extremely different, perhaps: There are grey kangaroos, but they are western grays, Macropus fuligi-nosus, a different species from the eastern gray (Macropus giganteus) that lives in the eastern states. The rosellas are different too. Where are the koalas? There aren't any. But there are those little red things with black and white stripes, numbats — none of them in the eastern states. But the plants are far more different — in fact, the southwest of Australia is famous for its bizarre and gorgeous array.

And go farther afield. Ujung Kulon National Park, in West Java, Indonesia, is a wonderful rainforest paradise, but what you will see there are peacocks, wild boar, monkeys, the wild cattle called banteng, and, if you are very lucky indeed, the Javan rhinoceros — not the ringtail possums, tree kangaroos, and rifle birds you see in a tropical rainforest at the same latitude in Australia. The animals in the Bwindi National Park, in Uganda, at the same latitude, are different again. Those in the Manu National Park in Peru are different yet again.

Although medieval Europeans were vaguely familiar with the animals and plants of North Africa and the Levant, it was not until Columbus's voyages in 1492 that it dawned on them that living organisms are not the same everywhere: There was a whole separate creation on the other side of the Atlantic! As European exploration progressed, it became obvious that there were not just one or two separate creations, but many. How to fit this into the story of Noah's Ark was a headache that remained until Darwin and his contemporaries — particularly the man who had very nearly been Darwin's nemesis but who became first his twin innovator and then his staunchest supporter, Alfred Russell Wallace.

Wallace and his contemporary, P.L. Sclater, and their successors mapped out and documented the distributions of terrestrial animals and plants across the globe and divided the land surface into faunal and floral regions. There are four major faunal realms, called Holarctic, Neotropical (or Neogaean), Paleotropical (or Afro-Tethyan), and Australian (or Notogaean). Each of these is divided and subdivided. There are six major floral kingdoms; four are the same as the faunal realms — Holarctic (or Boreal), Neotropical, Paleotropical, and Australian — but there are two others, whose past or present existence in the faunal sphere is a matter for discussion — Capensic (or South African) and Antarctic. It may simply be that animals are more mobile than plants and that any faunal element corresponding to the remarkable fynbos of the Western Cape, in South Africa, has long since been swamped, and that there are too few land animals capable of surviving the rigors of Antarctica and the subantarctic regions to form a fau-nal region of their own. These two differences apart, there is a pleasing correspondence between the faunal and floral realms — in outline but not in detail.

The study of the distribution of animals is called zoogeography, that of plants, phytogeography. Together, they make up the field of biogeography. We say that animals and plants that are restricted to particular places are endemic to those places, and for obvious reasons the idea of endemicity is central to biogeography.

There is more to biogeography than just noting with interest that kangaroos and eucalypts are found here and elephants and baobabs are found there. The hard part is finding out why. In the main, it is a compromise between past and present continental patterns, landforms, seaways, soils, and climate, spiced up by the abilities of animals and plants to move by themselves.

The Neotropical realm — South and Central America — has three layers of mammals: (1) The "old endemics" are the ones that are nothing like any mammals found anywhere else, like an order of placental mammals called Xenarthra, containing sloths, anteaters, and armadillos, and two orders of marsupials called Didelphimorphia and Paucituberculata — marsupials they may be, but these opossums and opossum rats are vastly different from the more familiar kangaroos, wombats, and "possums" of Australia. (2) The "young endemics" are the ones that belong to orders found elsewhere but that are represented in the Neotropics by special groups. There are two of these: the platyrrhines, or New World monkeys (marmosets, capuchins, howler and spider monkeys), and the caviomorphs, or New World rodents (tree porcupines, guinea pigs, coy-pus, and capybaras). (3) The "immigrants" are those that have very close relatives elsewhere: jaguars, pumas and ocelots; zorros, culpeos, and maned wolves; pampas deer, marsh deer, and brockets; and peccaries and tapirs.

It happens that we know a good deal about what South America was like in the past. Let us ignore the Age of Dinosaurs and begin after the asteroid hit, at the very beginning of the Age of Mammals, the Paleocene epoch, from 65 to 55 million years ago. South America is an island, separated from North America by a seaway at least as wide as that separating it from Africa. There, in fossil deposits of the period, are the old endemics: Xenarthra, the Didelphimorphia, and the Paucituberculata and a further array of sabertoothed marsupials and hoofed placentals, which are now dead and gone. Then the curtain closes, and we see no more for 30 million years.

Quite suddenly, the curtain opens again, on a Late Oligocene landscape, about 27 million years ago. The Paleocene collection are still there, but they have been joined by platyrrhines and caviomorphs. How they got there is deeply mysterious. As far as we know, South America had been unbrokenly an island — maybe the ancestors of the young endemics floated across the South Atlantic (which was only half its present width) from Africa on huge rafts of detached vegetation. We don't know. But there they suddenly are, and there they still are today.

At 5 million years ago, at the beginning of the Pliocene, it all changed dramatically, irreparably. Central America happened, a land bridge linking South America to North America. Now, North America had always been part of the rest of the world, with rest-of-the-world mammals. As soon as the land bridge arose, they jostled to get across it and try their luck against the long-isolated inhabitants of the long-isolated continent to the south. The sabertoothed marsupials and hoofed placentals crumbled before them. The other endemics survived, and many prospered; two, an armadillo and an opossum, even went the other way and are still spreading their range in North America.

And here the effect of present-day climate comes in, because South America always had a major tropical component, and Central America is tropical too. So the tropical vegetation spread into Central America, and even as far as the southeastern and southwestern coastal areas of Mexico. With them spread spider monkeys, howler monkeys, sloths, and other endemics.

Let us remind ourselves that human beings did not come down into the Neotropics along with the jaguar. They came later, in a much deadlier wave. What the Pliocene immigrants did for some of the old endemics, Homo sapiens is doing today to a far greater degree in sweeping the whole lot away — old endemics, new endemics, and immigrants alike.

It is astonishing that before Jonathan Kingdon, almost no one had thought of human evolution as having a biogeographical element (though we discovered just prior to publication that Juan Luis Arsuaga, in his book The Neanderthal's Necklace, published in 2001, also discusses this concept in depth). Kingdon's book, Lowly Origins, published in 2003, is going to make a lot of paleoanthropologists say, as Huxley did when he read Darwin's Origin of Species, "How extraordinarily stupid of me not to have thought of that myself!" Because, of course, humans and other apes are a Paleotropical group, and humans, chimpanzees, and gorillas belong to a specific part of it: the Afrotropical region. Today the Afrotropical region covers sub-Saharan Africa and coastal southern Arabia and appears to merge into the palearctic region (the Eurasian part of the Holarctic realm) along the Red Sea coast and into Israel. Here, African elephants, African buffaloes, hippos, black and white rhinos, servals, black-backed and side-striped jackals, spotted and brown hyenas, Cape hunting dogs, baboons, guenons, mangabeys, colobus monkeys, giraffes, and hordes and hordes of species of antelopes have their only home. Until recently, it seems that the lesser kudu and perhaps the giraffe extended into southwestern Arabia; the hamadryas baboon still does. Until recently the bubaline hartebeest lived in Israel; the Cape hyrax still does.

And hominines — gorilla, chimpanzee, and human — are Afrotropical. They evolved and diversified in the region, after splitting from the ancestors of their closest relative, the orangutan, in the Oriental region (the Indian and Southeast Asian part of the Paleotropical realm). It should not be too surprising, then, that the entire drama of proto-human diversification should have taken place in the Afrotropical region.

Gorillas (obligatorily) and chimpanzees (preferentially) are rainforest species; presumably, then, the earliest proto-humans were too. Where? The great rainforest belt of Central and West Africa, which pulsated back and forth as drier climate alternated with wetter, was already spoken for by gorillas and chimpanzees. But as Jonathan Kingdon points out, there is a neglected forest belt down the eastern seaboard of Africa. The eastern forests today are dissected fragments, but under a wetter climate regime they would be unified into a giant bloc, with fingers pushing inland alongside the major rivers — Juba, Tana, Galana, Pangani, Ruvuma, Zambezi, Limpopo, etc. Here is the best bet for a region where proto-humans separated from proto-chimpanzees, and here the more open nature of the forests — probably never real rainforests — selected for a ground-living ape more specialized than either of its closest relatives, which themselves are 50% or more terrestrial. And the gallery forests along the big rivers are the inland route opening out into the woodland and savanna habitat where we know the australop-ithecines best.

Look at a map: Israel, Lebanon, Syria, Turkey, and then we reach the Republic of Georgia. Dmanisi is 1000 km north of Israel, but in a warm phase, some of the Afrotropical fauna reached that far north. The fauna of Dmanisi, 1.7 million years ago, is dominated by Palearctic mammals like deer, bears, and marmots, but there are some Afrotropical elements, like ostriches and brown hyaenas. Like Israel today, the Georgian fauna then was mixed: perhaps, like Israel, Palearctic in the mountains, gazing down on Afrotropicals in the scorching lowlands below. Homo georgicus was perhaps at the extremity of its faunal region — but not beyond it. What we still don't know is whether the range of the species (or species group) contracted into Africa when the climate changed, or whether extremity living had enabled it to adapt to new zones and to push on east into the Oriental region.

We can ask the same question much much later. In the latest middle Pleistocene, newly evolved Homo sapiens extended its range into Israel (Qafzeh, Skhul) along with Afrotropical fauna when the climate there warmed up, and it gave place to Homo nean-derthalensis and Palearctic fauna (Tabun, Kebara, Amud) when the climate cooled down again. Eventually, as we know, the range of Homo sapiens did not recede back into Africa but pushed on into Europe. But was it able, 115,000 years ago, to push eastward? Is this when China and Southeast Asia were first populated by our own species, or did that event have to await a later push out of Africa? The fossil record of eastern Asia is not good enough to tell us.

In China the boundary between the Paleotropical and Holarctic realms is wide open. The Qinling Range, running east-west across the center, is the nearest thing to a bio-geographical boundary, but it is readily breached, and in the past, without a doubt, the boundary fluctuated according to climate. Presumably, early humans fluctuated with it, but at some point, a widening ecological tolerance enabled them to stay when the next cooling occurred, just as it did farther west, in Europe.

The most remarkable faunal boundary in the world bisects Indonesia. Between Borneo and Sulawesi runs Wallace's Line. West of it lies the Oriental region, with its tigers and leopards, civets and mongoose, squirrels, colugos, tree-shrews, and the Asian versions of elephants, rhinos, tapirs, and deer. East of it, in Sulawesi, live the dwarf buffalo known as anoa, the grotesque piglike babirusa, the extraordinary shrew mice, and the northwesternmost marsupials (two species groups of cuscus). Some 800 km east of that is another line, Lydekker's Line, east of which, in New Guinea, begins the real Australian fauna. Between Wallace's and Lydekker's lines is the region of Wallacea, but nobody knows what to do with it — is it Oriental or Australian? In fact, only Sulawesi has a substantial mammal fauna of its own. But as you go east through the Moluccas, what fauna there is becomes more and more Australian.

It is Wallace's Line that has attracted all the attention from an anthropological point of view because, after all, the main drift of people was from west to east across it: There was a time that western Indonesia (Sundaland) was occupied by human beings but New Guinea and Australia were not. Geologically, Sulawesi has been separate from Sundaland for quite a while — maybe since the Late Miocene — and the Makassar Strait, which separates it from Borneo, is very deep and, unlike the islands of Sundaland (and for that matter, New Guinea and Australia on the other side of Lydekker's Line), the two would not have been joined at times of low sea level.

When and how did people first cross Wallace's line?

Great excitement was caused in the 1990s when Dutch, Australian, and Indonesian teams found human artifacts on the island of Flores, dating to nearly 800,000 years ago — because Flores lies east of Wallace's Line! As a matter of fact, Wallace's Line is much less substantial to the south than it is farther north; it is reputed to run between Bali and Lombok. It is true that Bali is part of Sundaland and was connected to Java and thence to Sumatra, Borneo, and the Asian mainland when the sea level was low, whereas the narrow straits between Bali and Lombok are very deep. But it turns out that Lombok shares more of its mammals with Bali than we once thought. It looks as much like a climatic difference as a strictly biogeographical one, and the Oriental fauna dies away successively from west to east as the climate gets drier: West Java, East Java, Bali, Lombok, Sumbawa. Maybe the Lombok Strait was deepened by tectonic activity fairly recently in this highly tectonically active part of the world? Still, east of Sumbawa is another narrow but deep strait, and then we get Flores and its offshore islands. And Flores does have a little mammalian fauna of its own (consisting almost entirely of funny rats, including a wonderful giant one, Papagomys armandvillei, half a meter long, excluding the tail). So there is reason to think that humans, more than three-quarters of a million years ago, wandered unusually far east, crossing the sea as they did so. Does this mean that they had boats? We don't know. But the only humans in Southeast Asia at the time, as far as we knew, were Homo erectus. So our beetle-browed cousin was not such a slouch after all. But stand by for further, stunning evidence from Flores ...

There is not a scrap of evidence that anyone got farther east or southeast until much later. The sea gaps between Timor and Australia and New Guinea, even between Flores and Timor, are really, really substantial. To cross them — that was Homo sapiens' work.

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