Faysal Bibi

Ecological change in the lower Omo Valley around 2.8 Ma

Late Pliocene climate changes have long been implicated in environmental changes and mammalian evolution in Africa, but high-resolution examinations of the fossil and climatic records have been hampered by poor sampling. By using fossils from the well-dated Shungura Formation (lower Omo Valley, northern Turkana Basin, southern Ethiopia), we investigate palaeodietary changes in one bovid and in one suid lineage from 3 to 2 Ma using stable isotope analysis of tooth enamel. Results show unexpectedly large increases in C4 dietary intake around 2.8 Ma in both the bovid and suid, and possibly in a previously reported hippopotamid species. Enamel δ13C values after 2.8 Ma in the bovid (Tragelaphus nakuae) are higher than recorded for any living tragelaphin, and are not expected given its conservative dental morphology. A shift towards increased C4 feeding at 2.8 Ma in the suid (Kolpochoerus limnetes) appears similarly decoupled from a well-documented record of dental evolution indicating gradual and progressive dietary change. The fact that two, perhaps three, disparate Pliocene herbivore lineages exhibit similar, and contemporaneous changes in dietary behaviour suggests a common environmental driver. Local and regional pollen, palaeosol and faunal records indicate increased aridity but no corresponding large and rapid expansion of grasslands in the Turkana Basin at 2.8 Ma. Our results provide new evidence supporting ecological change in the eastern African record around 2.8 Ma, but raise questions about the resolution at which different ecological proxies may be comparable, the correlation of vegetation and faunal change, and the interpretation of low δ13C values in the African Pliocene.

Mio-Pliocene Faunal Exchanges and African Biogeography: The Record of Fossil Bovids

The development of the Ethiopian biogeographic realm since the late Miocene is here explored with the presentation and review of fossil evidence from eastern Africa. Prostrepsiceros cf. vinayaki and an unknown species of possible caprin affinity are described from the hominid-bearing Asa Koma and Kuseralee Members (∼5.7 and ∼5.2 Ma) of the Middle Awash, Ethiopia. The Middle Awash Prostrepsiceros cf. vinayaki constitutes the first record of this taxon from Africa, previously known from the Siwaliks and Arabia. The possible caprin joins a number of isolated records of caprin or caprin-like taxa recorded, but poorly understood, from the late Neogene of Africa. The identification of these two taxa from the Middle Awash prompts an overdue review of fossil bovids from the sub-Saharan African record that demonstrate Eurasian affinities, including the reduncin Kobus porrecticornis, and species of Tragoportax. The fossil bovid record provides evidence for greater biological continuity between Africa and Eurasia in the late Miocene and earliest Pliocene than is found later in time. In contrast, the early Pliocene (after 5 Ma) saw the loss of any significant proportions of Eurasian-related taxa, and the continental dominance of African-endemic taxa and lineages, a pattern that continues today.

Bovidae (Mammalia: Artiodactyla) from the late Miocene of Sivas, Turkey

Abstract Craniodental remains of fossil bovids from the late Miocene İncesu Formation, from sites near the city of Sivas, Turkey, are described. The bovid remains represent at least five species: Gazella cf. G. capricornis, Prostrepsiceros houtumschindleri syridisi, cf. Protoryx sp., Tethytragus cf. T. koehlerae, and Tragoportax cf. T. amalthea. The Sivas fossil bovid assemblage is fairly typical for the Greco-Iranian-Afghan paleobiological province, and compares well with the classic Turolian sites of Samos, Pikermi, and Maragheh. Biochronological correlations using these fossil bovids suggest the Sivas fossil assemblage is MN11 or early MN12 in age, or somewhere between 9–7 Ma. The presence of Tethytragus at Sivas represents only the second occurrence of this typically mid-Miocene (MN5–8) taxon from the late Miocene. Paleoecological attributes of the Sivas fossil bovids suggest local paleoenvironments at Sivas comprised shrubland to woodland biomes, perhaps devoid of expansive grasslands or dense forests. The presence/absence and relative abundances of bovid taxa within and among different Greek and Anatolian late Miocene fossil sites is compared and contrasted by way of correspondence analysis. Sivas plots among a number of sites all characterized by high proportions of Gazella, Tragoportax, and Protoryx/Pachytragus, and these in turn are readily distinguished from sites in which Palaeoreas/Majoreas, Protragelaphus, Oioceros, and Miotragocerus are more common. It is suggested that Sivas and similar sites (e.g. Sinap, Akkaşdağı) may have sampled drier, more open habitats than those with strongly differing faunal compositions (e.g. Nikiti-1, Çorakyerler).

Late Pliocene Fossiliferous Sedimentary Record and the Environmental Context of early Homo from Afar, Ethiopia

Finding Homo nearly 3 million years ago The fossil record of humans is notoriously patchy and incomplete. Even so, skeletal remains and artifacts unearthed in Africa in recent decades have done much to illuminate human evolution. But what is the origin of the genus Homo? Villmoare et al. found a fossil mandible and teeth from the Afar region in Ethiopia. The find extends the record of recognizable Homo by at least half a million years, to almost 2.8 million years ago. The morphological traits of the fossil align more closely with Homo than with any other hominid genus. DiMaggio et al. confirm the ancient date of the site and suggest that these early humans lived in a setting that was more open and arid than previously thought. Science, this issue p. 1352, p. 1355 Sediments from the Lee Adoyta site in Ethiopia suggest that early Homo lived in open and arid conditions. Sedimentary basins in eastern Africa preserve a record of continental rifting and contain important fossil assemblages for interpreting hominin evolution. However, the record of hominin evolution between 3 and 2.5 million years ago (Ma) is poorly documented in surface outcrops, particularly in Afar, Ethiopia. Here we present the discovery of a 2.84– to 2.58–million-year-old fossil and hominin-bearing sediments in the Ledi-Geraru research area of Afar, Ethiopia, that have produced the earliest record of the genus Homo. Vertebrate fossils record a faunal turnover indicative of more open and probably arid habitats than those reconstructed earlier in this region, which is in broad agreement with hypotheses addressing the role of environmental forcing in hominin evolution at this time. Geological analyses constrain depositional and structural models of Afar and date the LD 350-1 Homo mandible to 2.80 to 2.75 Ma.

An ecometric analysis of the fossil mammal record of the Turkana Basin

Although ecometric methods have been used to analyse fossil mammal faunas and environments of Eurasia and North America, such methods have not yet been applied to the rich fossil mammal record of eastern Africa. Here we report results from analysis of a combined dataset spanning east and west Turkana from Kenya between 7 and 1 million years ago (Ma). We provide temporally and spatially resolved estimates of temperature and precipitation and discuss their relationship to patterns of faunal change, and propose a new hypothesis to explain the lack of a temperature trend. We suggest that the regionally arid Turkana Basin may between 4 and 2 Ma have acted as a ‘species factory’, generating ecological adaptations in advance of the global trend. We show a persistent difference between the eastern and western sides of the Turkana Basin and suggest that the wetlands of the shallow eastern side could have provided additional humidity to the terrestrial ecosystems. Pending further research, a transient episode of faunal change centred at the time of the KBS Member (1.87–1.53 Ma), may be equally plausibly attributed to climate change or to a top-down ecological cascade initiated by the entry of technologically sophisticated humans. This article is part of the themed issue ‘Major transitions in human evolution’.

BIOSTRATIGRAPHY AND MAGNETOSTRATIGRAPHY OF THE MID-MIOCENE RAILROAD CANYON SEQUENCE, MONTANA AND IDAHO, AND AGE OF THE MID-TERTIARY UNCONFORMITY WEST OF THE CONTINENTAL DIVIDE

Abstract The Barstovian of the northern Rocky Mountains, U.S.A., is known mainly from deposits east of the continental divide; this article provides new information from west of the divide. The biostratigraphic, geologic, magnetostratigraphic, and lithostratigraphic setting is reported for an unusually complete Arikareean, Hemingfordian, and Barstovian stratigraphic section known as the Railroad Canyon Sequence in Montana and Idaho. At least 35 taxa of fossil vertebrates collected from 50 different localities are placed in stratigraphic context. Lithostratigraphic attributes indicate the presence of a freshwater lake during the Arikareean, intermittent saline lakes through much of the Hemingfordian, a late Hemingfordian unconformity (the Mid-Tertiary Unconformity), and absence of persistent lakes through the Barstovian. The sequence records the development of increasingly arid conditions in the depositional basin. A change in bedding attitude and generally coarser sediments above the Mid-Tertiary Unconformity indicate uplift of the region during the Barstovian, possibly accompanied by slight structural tilting. The analysis helps date Barstovian faunas, and provides a useful tie point for correlating the Barstovian Land-Mammal Age to the magnetostratigraphic and radioisotopic scale in the western Rockies, and ultimately to the Global Polarity Time Scale (GPTS). It also suggests that the Mid-Tertiary unconformity is approximately coeval on the eastern and western flanks of the mountains, supporting tectonic models that require regional uplift between ca. 16.8 and 17.5 Ma.

New geological and palaeontological age constraint for the gorilla–human lineage split

The palaeobiological record of 12 million to 7 million years ago (Ma) is crucial to the elucidation of African ape and human origins, but few fossil assemblages of this period have been reported from sub-Saharan Africa. Since the 1970s, the Chorora Formation, Ethiopia, has been widely considered to contain ~10.5 million year (Myr) old mammalian fossils. More recently, Chororapithecus abyssinicus, a probable primitive member of the gorilla clade, was discovered from the formation. Here we report new field observations and geochemical, magnetostratigraphic and radioisotopic results that securely place the Chorora Formation sediments to between ~9 and ~7 Ma. The C. abyssinicus fossils are ~8.0 Myr old, forming a revised age constraint of the human–gorilla split. Other Chorora fossils range in age from ~8.5 to 7 Ma and comprise the first sub-Saharan mammalian assemblage that spans this period. These fossils suggest indigenous African evolution of multiple mammalian lineages/groups between 10 and 7 Ma, including a possible ancestral-descendent relationship between the ~9.8 Myr old Nakalipithecus nakayamai and C. abyssinicus. The new chronology and fossils suggest that faunal provinciality between eastern Africa and Eurasia had intensified by ~9 Ma, with decreased faunal interchange thereafter. The Chorora evidence supports the hypothesis of in situ African evolution of the Gorilla–Pan–human clade, and is concordant with the deeper divergence estimates of humans and great apes based on lower mutation rates of ~0.5 × 10−9 per site per year (refs 13, 14, 15).

Early evidence for complex social structure in Proboscidea from a late Miocene trackway site in the United Arab Emirates

Many living vertebrates exhibit complex social structures, evidence for the antiquity of which is limited to rare and exceptional fossil finds. Living elephants possess a characteristic social structure that is sex-segregated and multi-tiered, centred around a matriarchal family and solitary or loosely associated groups of adult males. Although the fossil record of Proboscidea is extensive, the origin and evolution of social structure in this clade is virtually unknown. Here, we present imagery and analyses of an extensive late Miocene fossil trackway site from the United Arab Emirates. The site of Mleisa 1 preserves exceptionally long trackways of a herd of at least 13 individuals of varying size transected by that of a single large individual, indicating the presence of both herding and solitary social modes. Trackway stride lengths and resulting body mass estimates indicate that the solitary individual was also the largest and therefore most likely a male. Sexual determination for the herd is equivocal, but the body size profile and number of individuals are commensurate with those of a modern elephant family unit. The Mleisa 1 trackways provide direct evidence for the antiquity of characteristic and complex social structure in Proboscidea.

Early guenon from the late Miocene Baynunah Formation, Abu Dhabi, with implications for cercopithecoid biogeography and evolution

Significance The primate subfamily Cercopithecinae represents the most diverse and successful living Old World primate group, with a current distribution throughout Africa and Asia. However, how and when these monkeys dispersed out of Africa is not well understood. This paper is significant in its description of a ∼6.5–8.0 million-y-old fossil guenon from Arabia representing the earliest cercopithecine (and only guenon) yet known outside of Africa. Furthermore, this specimen extends the guenon fossil record by at least 2.3 million y and may represent the earliest known cercopithecine as well. Because Old World monkeys appear to have dispersed out of Africa sometime during the Late Miocene, the Arabian fossils also have implications for dispersal scenarios in Old World monkey biogeography and evolution. A newly discovered fossil monkey (AUH 1321) from the Baynunah Formation, Emirate of Abu Dhabi, United Arab Emirates, is important in a number of distinct ways. At ∼6.5–8.0 Ma, it represents the earliest known member of the primate subfamily Cercopithecinae found outside of Africa, and it may also be the earliest cercopithecine in the fossil record. In addition, the fossil appears to represent the earliest member of the cercopithecine tribe Cercopithecini (guenons) to be found anywhere, adding between 2 and 3.5 million y (∼50–70%) to the previous first-appearance datum of the crown guenon clade. It is the only guenon—fossil or extant—known outside the continent of Africa, and it is only the second fossil monkey specimen so far found in the whole of Arabia. This discovery suggests that identifiable crown guenons extend back into the Miocene epoch, thereby refuting hypotheses that they are a recent radiation first appearing in the Pliocene or Pleistocene. Finally, the new monkey is a member of a unique fauna that had dispersed from Africa and southern Asia into Arabia by this time, suggesting that the Arabian Peninsula was a potential filter for cross-continental faunal exchange. Thus, the presence of early cercopithecines on the Arabian Peninsula during the late Miocene reinforces the probability of a cercopithecoid dispersal route out of Africa through southwest Asia before Messinian dispersal routes over the Mediterranean Basin or Straits of Gibraltar.

Unraveling bovin phylogeny: accomplishments and challenges

The phylogenetic systematics of bovin species forms a common basis for studies at multiple scales, from the level of domestication in populations to major cladogenesis. The main big-picture accomplishments of this productive field, including two recent works, one in BMC Genomics, are reviewed with an eye for some of the limitations and challenges impeding progress. See Research article http://www.biomedcentral.com/1471-2164/10/177