Human taxonomic diversity in the pleistocene: Does Homo erectus represent multiple hominid species?

Recently, nomina such as “Homo heidelbergensis” and “H. ergaster” have been resurrected to refer to fossil hominids that are perceived to be specifically distinct from Homo sapiens and Homo erectus. This results in a later human fossil record that is nearly as speciose as that documenting the earlier history of the family Hominidae. However, it is agreed that there remains only one extant hominid species: H. sapiens. Has human taxonomic diversity been significantly pruned over the last few hundred millennia, or have the number of taxa been seriously overestimated? To answer this question, the following null hypothesis is tested: polytypism was established relatively early and the species H. erectus can accommodate all spatio-temporal variation from ca. 1.7 to 0.5 Ma. A disproof of this hypothesis would suggest that modern human polytypism is a very recent phenomenon and that speciation throughout the course of human evolution was the norm and not the exception. Cranial variation in a taxonomically mixed sample of fossil hominids, and in a modern human sample, is analyzed with regard to the variation present in the fossils attributed to H. erectus. The data are examined using both univariate (coefficient of variation) and multivariate (determinant) analyses. Employing randomization methodology to offset the small size and non-normal distribution of the fossil samples, the CV and determinant results reveal a pattern and degree of variation in H. erectus that most closely approximates that of the single species H. sapiens. It is therefore concluded that the null hypothesis cannot be rejected. © 1993 Wiley-Liss, Inc.     

A Homo habilis maxilla and other newly-discovered hominid fossils from Olduvai Gorge, Tanzania

In 1995, a 1.8 million year old hominid maxilla with complete dentition (OH 65) was excavated from Bed I in the western part of Olduvai Gorge. The molar crowns are small relative to the long flaring roots, and the root of the canine is very long and straight. The broad maxilla with wide U-shaped palate and the form of the tooth roots closely match those of KNM-ER 1470 which, in its parietal size and morphology, matches the type specimen of Homo habilis, OH 7. Thus, OH 65 and KNM-ER 1470 group with OH 7 as representatives of H. habilis while some other Olduvai specimens, such as OH 13 and OH 24, have more in common in terms of morphology and brain size with Australopithecus africanus. Between 1995 and 2007, the OLAPP team has recovered teeth of eight other hominid individuals from various parts of Olduvai Gorge. These have been identified as belonging to H. habilis, Paranthropus boisei, and Australopithecus cf. africanus.     

New Australopithecus boisei calvaria from East Lake Turkana,Kenya

The calvaria of an adult Australopithecus boisei from Area 104, Koobi Fora, Lake Turkana, is described. The specimen, KNM-ER 23000, comes from sediments dated to about 1.9 Ma. It consists of the frontal, both parietals, both temporals, most of the occipital as well as two small pieces of sphenoid, and a mandibular tooth root. The specimen is presumed to be an adult male, based on its size and the great development of features associated with the masticatory apparatus. KNM-ER 23000 is close in general size and shape to KNM-ER 406, KNM-ER 13750, and Olduvai Hominid 5 and it has a mixture of features seen in these three roughly contemporaneous crania. The frontal, especially the tori, resembles that of OH 5; the parietals are most like those of KNM-ER 13750; the occipital is like those of the two other Turkana specimens, and the temporals have a mixture of features from all of these, This specimen adds to our knowledge of variability in A. boisei. © 1993 Wiley-Liss, Inc.     

Taxonomic status of the hominid mandible KNM-ER TI 13150 from the middle pliocene of tabarin,in Kenya

A partial mandible with two molars intact was recovered between 1981 and 1984 from deposits of the Middle Pliocene at Tabarin, in Kenya. It has been described and assigned toAustralopithecus cf.afarensis Johanson, White, andCoppens, 1978, with the condition that if ‘A. afarensis’ is revised, then the attribution may change. The taxon ‘A. afarensis’ was found to be invalid and was revised. The smaller specimens of ‘A. afarensis,’ to which the Tabarin mandible was said to be similar, were redescribed asHomo antiquus Ferguson, 1984. Since the Tabarin mandible andH. antiquus are successive transients of the same gens and are allopatric, the Tabarin hominid population is described as an earlier chronosubspecies,Homo antiquus praegens ssp. n.     

Preliminary observations on the BK 8518 mandible from Baringo, Kenya

A newly discovered adult hominid mandible (BK 8518) from Baringo, Kenya, is described and assessed. The corpus, many of the tooth crowns, and most of the left ascending ramus are preserved. The teeth are heavily and asymmetrically worn. Compared with BK 67 (the 1966 mandible) the body of BK 8518 is more robust; the internal symphyseal buttressing is more pronounced; the M3s have seven cusps and exceed the M2s in size. There are no compelling reasons, however, to attribute the two mandibles to different taxa and, in view of the lack of any comprehensive taxonomic diagnosis for Homo erectus, "erectus-like," and habiline mandibular remains, the new specimen is also best regarded as Homo sp. indet. (aff. erectus).     

New hominid fossils from the Swartkrans formation (1979-1986 excavations): craniodental specimens

Seventy-two individually numbered hominid craniodental fossils from recent excavations at Swartkrans are described. All derive from in situ decalcified breccia and/or unconsolidated sediments. A total of 20 specimens, representing 13 to 16 individuals derive from Member 1 "Lower Bank," two teeth derive from sediments along the Member 1-2 Interface, 38 fossils representing 19 to 24 individuals come from Member 2, and 12 teeth representing 9 to 11 individuals derive from Member 3. All but four of the specimens are attributable at the generic level; one specimen from Member 1 "Lower Bank" and five specimens from Member 2 are attributed to Homo, while the others represent Paranthropus. The proportional representation of Homo in the Swartkrans Formation is markedly higher in Member 2 (c. 33%) than in the Member 1 "Lower Bank" (c. 8%) and Member 1 "Hanging Remnant" (c. 5%) samples.     

African ape ancestry

It is commonly believed that the australopithecines are more closely related to humans than to African apes. This view is hardly compatible with the biomolecular data which place theHomo/Pan split at the beginning of the australopithecine period. Nothing in the fossil hominid morphology precludes the possibility that some australopithecines were ancestral to gorillas or chimpanzees and others to humans.     

The endocast from Dana Aoule North (DAN5/P1): A 1.5 million year-old human braincase from Gona,Afar, Ethiopia

The nearly complete cranium DAN5/P1 was found at Gona (Afar, Ethiopia), dated to 1.5–1.6 Ma, and assigned to the species Homo erectus. Its size is, nonetheless, particularly small for the known range of variation of this taxon, and the cranial capacity has been estimated as 598 cc. In this study, we analyzed a reconstruction of its endocranial cast, to investigate its paleoneurological features. The main anatomical traits of the endocast were described, and its morphology was compared with other fossil and modern human samples. The endocast shows most of the traits associated with less encephalized human taxa, like narrow frontal lobes and a simple meningeal vascular network with posterior parietal branches. The parietal region is relatively tall and rounded, although not especially large. Based on our set of measures, the general endocranial proportions are within the range of fossils included in the species Homo habilis or in the genus Australopithecus. Similarities with the genus Homo include a more posterior position of the frontal lobe relative to the cranial bones, and the general endocranial length and width when size is taken into account. This new specimen extends the known brain size variability of Homo ergaster/erectus, while suggesting that differences in gross brain proportions among early human species, or even between early humans and australopiths, were absent or subtle.     

Posterior tooth size, body size, and diet in South African gracile Australopithecines

A model relating relative size of the posterior teeth to diet is suggested for forest and savanna primates and Homo. Relative tooth size is calculated for the South African gracile australopithecine sample using posterior maxillary area sums and size estimates based on four limb bones. A number of limbs were shown to be non-hominid. Comparisons show the South African gracile sample apparently adapted to a very heavily masticated diet with relative tooth size significantly greater than any living hominoid. Periodic intensive utilization of grains and roots combined with scavenged animal protein are suggested as the most likely dietary reconstruction.     

Investigation into the relationship between perikymata counts and crown formation times

This study reports on a sample of 12 modern human incisors (from two archaeological sites) that were viewed with a scanning electron microscope and whose perikymata were counted. These 12 incisors more than doubles the previously published sample size of modern human incisors that have served as the published standard for perikymata number in human incisors and have been employed to define taxonomic relationships in fossil hominids. All previously published fossil specimens fall within the expanded range of modern human perikymata counts and can no longer be considered distinctively nonhuman in dental formation time. Five neandertal incisors from the Krapina site in Croatia, Yugoslavia, were also examined. These incisors substantially expand the previous data base for counts of perikymata in Homo sapiens neanderthalensis, likewise overlapping the previously published modern human range. Finally, the validity of methods that have been employed for deriving crown formation times from perikymata counts in fossil hominines is called into question. Utilizing the presently known perikymata ranges for modern humans, these methods do not predict the range of known crown formation times of modern humans as assessed from studies of living children.     

Homo erectus—who,when and where: A survey

The state of information bearing on Homo erectus as developed since about 1960 is surveyed, with the resulting effects on problems. Definitions of H. erectus still rest on the Far Eastern samples (Chou-k'ou-tien/Java), and thus relate to late Lower to middle Middle Pleistocene material. Numerous important individual finds, however, have expanded the total: extension of the early and very early Sangiran material; very early to later in Africa, and relatively late in Europe. Datings remain uncertain or controversial within broad limits, but with some important successes and revisions. Discussion by authors of problems concerns degree of divergence among H. erectus populations and rate of evolutionary change; both appear relatively slight, but the data are inadequate for much present judgment. The apparent zone of transition to more advanced morphology (H. sapiens, sensu lato) by the late Middle Pleistocene better reflects signs of regional divergence. Some writers—not all—believe that even the earliest European fossils known (e.g., Petralona) had already advanced to a H. sapiens basic level, with later change in the direction of Neanderthals. A separate African phylum, from OH 9, is also suggested; recent Chinese finds may provide a third different post-erectus population before the Upper Pleistocene. Taxonomic expression of all this gives some problems.     

Multiple dispersals and modern human origins

Despite a massive endeavour, the problem of modern human origins not only remains unresolved, but is usually reduced to “Out of Africa” versus multiregional evolution. Not all would agree, but evidence for a single recent origin is accumulating. Here, we want to go beyond this debate and explore within the “Out of Africa” framework an issue that has not been fully addressed: the mechanism by which modern human diversity has developed. We believe there is no clear rubicon of modern Homo sapiens, and that multiple dispersals occurred from a morphologically variable population in Africa. Pre-existing African diversity is thus crucial to the way human diversity developed outside Africa. The pattern of diversity—behavioural, linguistic, morphological and genetic—can be interpreted as the result of dispersals, colonisation, differentiation and subsequent dispersals overlaid on former population ranges. The first dispersals would have originated in Africa from where two different geographical routes were possible, one through Ethiopia/Arabia towards South Asia, and one through North Africa/Middle East towards Eurasia.     

Human evolution

The common ancestor of modern humans and the great apes is estimated to have lived between 5 and 8 Myrs ago, but the earliest evidence in the human, or hominid, fossil record is Ardipithecus ramidus, from a 4.5 Myr Ethiopian site. This genus was succeeded by Australopithecus, within which four species are presently recognised. All combine a relatively primitive postcranial skeleton, a dentition with expanded chewing teeth and a small brain. The most primitive species in our own genus, Homo habilis and Homo rudolfensis, are little advanced over the australopithecines and with hindsight their inclusion in Homo may not be appropriate. The first species to share a substantial number of features with later Homo is Homo ergaster, or ‘early African Homo erectus’, which appears in the fossil record around 2.0 Myr. Outside Africa, fossil hominids appear as Homo erectus-like hominids, in mainland Asia and in Indonesia close to 2 Myr ago; the earliest good evidence of ‘archaic Homo’ in Europe is dated at between 600–700 Kyr before the present. Anatomically modern human, or Homo sapiens, fossils are seen first in the fossil record in Africa around 150 Kyr ago. Taken together with molecular evidence on the extent of DNA variation, this suggests that the transition from ‘archiac’ to ‘modern’ Homo may have taken place in Africa.     

Fire resilience of ant assemblages in long‐unburnt savanna of northern Australia

Abstract Tropical savannas and rainforests contrast in their flammability and the fire resilience of their associated species. While savanna species generally exhibit high resilience to burning, there is much debate about the fire resilience of forest‐associated species, and the persistence of forest patches in a flammable savanna matrix. Where fire has been excluded, savanna tends on a trajectory towards forest, with an increase in forest‐associated plants and animal species. This study tested the idea that given the high proportion of forest‐associated taxa in long‐unburnt savanna, the fauna of these areas would be expected to exhibit less resilience to fire than the fauna in frequently burnt savannas. The study investigated the immediate and short‐term effects on ant assemblages of re‐introducing fire into long‐unburnt savanna in northern Australia. The ant fauna exhibited high resistance to fires, with no significant short‐term change in mean abundance or species richness; instead, seasonality had a far stronger influence on overall ant activity. Fire caused dramatic declines in dominance of the patchily distributed forest‐associated species Oecophylla smaragdina and Papyrius sp., but had no effect on overall dominance by open savanna species of Iridomyrmex. Dominance by Iridomyrmex pallidus declined, but this was compensated for by increases in I. reburrus, while two other species of Iridomyrmex showed no change. This indicates a high level of functional redundancy among dominant species of Iridomyrmex, which universally dominate open savanna communities, but not of dominant forest‐associated species. Overall, our findings demonstrate a high degree of fire‐resilience of the long‐unburnt savanna ant fauna. Despite the occurrence of forest‐associated species, the high proportion of savanna species persisting in this habitat means that long‐unburnt savanna retains the general response characteristics of frequently burnt savanna.     

Affinities of the Swartkrans 847 hominid cranium

Further evidence of the presence of a second hominid species at the Swartkrans locality was obtained in 1969 when the SK.847 specimen was discovered by us to represent the same individual as the SK.80 maxilla. The SK.847 specimen had previously been regarded as robust australopithecine, whereas the latter was first attributed to Telanthropus capensis and subsequently to a species of the genus Homo. Recent criticism of our interpretation of these remains has not evaluated and analyzed critically the primary fossil evidence. Instead it relies on a strict adherence to an as yet unsubstantiated hypothesis that posits only a single hominid species at any point in space and time in the Cenozoic history of Hominidae.     

Modification of Anopheles gambiae distribution at high altitudes in Madagascar

In Madagascar, Anopheles gambiae has been found below altitudes of 1,000 m. We sampled An. gambiae sensu lato (sl) between 2008 and 2010 in the Central Highlands of Madagascar at altitudes over 1,200 m. The study site consists of rainforest, rainforest edge, and an open savanna biotope. Anopheles gambiae and An. arabiensis, as well as molecular forms of An. gambiae, were identified molecularly. An. gambiae accounted for 26.7% at the edge of the rainforest and 2.3% in the open savanna biotope. One specimen of this species was caught in the forest. An. arabiensis accounted for 66.3% at the edge of the rainforest and 97.7 % in the open savanna biotope. All An. gambiae adults tested belonged to the S molecular form. An. gambiae is present at high altitudes in Madagascar, with a high prevalence at the rainforest edge. Several factors, including the appearance of new favorable biotopes, recolonization after a reduction of indoor vector control, and climate change, may contribute to its distribution. The changing distribution of An. gambiae may have consequences for the distribution and incidence of malaria in the Malagasy Highlands.     

Homo erectus: Ancestor or evolutionary side branch?

Controversies in paleoanthropology wax and wane, but substantial interest is currently focused on Homo erectus. This species has traditionally been regarded as a member in good standing of the human family, where it is placed as an evolutionary intermediate between earlier Homo habilis and later Homo sapiens. Recently, however, some workers have questioned whether the species exists at all. If its populations have been transformed slowly toward the modern condition, and if continuity with living people can be demonstrated in many geographic regions, then any separation of Homo erectus from Homo sapiens must be largely arbitrary. In that case, only one species should be recognized and this slowly changing lineage would have to be called Homo sapiens. Other paleontologists adopt a different view, arguing that Homo erectus is not only anatomically distinctive but also restricted in its geographic distribution. They claim that the fossils from Java and China are so specialized in appearance that they cannot lie in the mainstream of human evolution. Homo erectus, strictly defined as limited to the Far East, probably went extinct without issue. If so, more modern populations must have evolved from another source, perhaps one outside of Asia altogether.     

Nasal morphology and the emergence of Homo erectus

Modern humans, among extant hominoids, possess a unique projecting, external nose whose basic structure is reflected in a series of skeletal features including nasal bone convexity, an internasal angle, lateral nasal aperture eversion, prominence and anterior positioning of the anterior nasal spine, an acute angle of the subnasal alveolar clivus, and an expansion of the breadth of the nasal bones relative to that of the piriform aperture. This anatomy appears with the emergence of Homo erectus ca. 1.6 million years ago. Although it undoubtedly evolved in the context of craniofacial and dental reduction during hominid evolution, it appears to have been primarily a response to the need for moisture conservation in an arid environment via turbulence enhancement and ambient cooling of expired air. Its appearance at this time in hominid evolution, in conjunction with the presence of a fatigue-resistant locomotor anatomy characteristic of archaic members of the genus Homo, indicates a shift to increasingly prolonged bouts of activity in open and arid environments.     

Hominid-pongid distinctiveness in the miocene-pliocene fossil record: The lothagam mandible

The Lothagam mandibular fragment, found in 1967 west of Lake Turkana, Kenya, has been dated to 5.5 million years ago. This date is significant because it may lie within the suggested time range during which the hominid and pongid clades diverged. Because of its fragmentary condition and great age, this specimen has run the gamut of taxonomic assignations, from ramapithecine to pongid to hominid. These three nomenclatural categories serve as the basis for three hypotheses tested in this study. First, morphological and metric comparisons between Lothagam and a sample of Euroafrican ramapithecines address the hypothesis of “Lothagam as predi-vergence hominoid.” Second, comparisons with a sample of Pan test the “Lothagam as postdivergence, African protopongid” hypothesis. Finally, samples of Australopithecus afarensis and A. africanus were utilized to evaluate the hypothesis of “Lothagam as postdivergence, early hominid.” Unlike previous studies attempting to ascertain the evolutionary affinities of this enigmatic fossil, this work benefits from the large sample of A. afarensis specimens now generally available for study. Metric and morphological comparisons demonstrate Lothagam's affinity to A. afarensis in sharing derived, hominid states in such features as the mental foramen vertical position, the ascending ramus origin, the breadth of the alveolar margin, the reduction of the hypoconulid, the dimensions of the M₁ and the dimensions of the mandibular corpus. It is suggested that the dental/gnathic features enumerated in this study can be employed to distinguish ancestral hominid from pongid in future Mio/Pliocene paleontological discoveries.     

Volumetric and asymmetry determinations on recent hominid endocasts: Spy I and II,Djebel Ihroud I,and the salè Homo erectus specimens,with some notes on neandertal brain size

Full brain endocast reconstructions of the Neandertals, Spy I and II, Djebel Ihroud I, and the Homo erectus specimen from Salè, Morocco have yielded accurate volumes. Spy I = 1,305 ml; Spy II = 1,553 ml; Djebel Ihroud I = 1,305 ml; Salè = 880 ml. While there are no remarkable gyral and sulcal patterns one can delineate, the brain endocasts do show evidence of left-occipital, right-frontal petalias, suggesting right-handedness, and possibly human cognitive specialization, involving symbol processing and visuospatial integration. Some speculations regarding Neandertal brain size are also offered, in which it is suggested that their possibly larger brain sizes were related to greater muscularity than in modern Homo sapiens.