The skeletal remains of Pleistocene anatomically modern humans are rare in island Southeast Asia. Moreover, continuing doubts over the dating of most of these finds has left the arrival time for the region's earliest inhabitants an open question. The unique biogeography of island Southeast Asia also raises questions about the physical and cultural adaptations of early anatomically modern humans, especially within the setting of rainforest inhabitation. Within this context the Deep Skull from the West Mouth of the Niah Caves continues to figure prominently owing to its relative completeness and the greater certainty surrounding its geological age. Recovered along with this partial cranium in 1958 were several postcranial bones including a partial femur which until now has received little attention. Here we provide a description and undertake a comparison of the Deep Skull femur finding it to be very small in all of its cross-sectional dimensions. We note a number of size and shape similarities to the femora of Indigenous Southeast Asians, especially Aeta people from the Philippines. We estimate its stature to have been roughly 145-146 cm and body mass around 35 kg, confirming similarities to Aeta females. Its extreme gracility indicated by low values for a range of biomechanical parameters taken midshaft meets expectations for a very small (female) Paleolithic East Asian. Interestingly, the second moment of area about the mediolateral axis is enlarged relative to the second moment of area about the anteroposterior axis, which could potentially signal a difference in activity levels or lifestyle compared with other Paleolithic femora. However, it might also be the result of sexual dimorphism in these parameters as well as possibly reflecting changes associated with aging.
Cambay amber originates from the warmest period of the Eocene, which is also well known for the appearance of early angiosperm-dominated megathermal forests. The humid climate of these forests may have triggered the evolution of epiphytic lineages of bryophytes; however, early Eocene fossils of bryophytes are rare. Here, we present evidence for lejeuneoid liverworts and pleurocarpous mosses in Cambay amber. The preserved morphology of the moss fossil is inconclusive for a detailed taxonomic treatment. The liverwort fossil is, however, distinctive; its zig-zagged stems, suberect complicate-bilobed leaves, large leaf lobules, and small, deeply bifid underleaves suggest a member of Lejeuneaceae subtribe Lejeuneinae (Harpalejeunea, Lejeunea, Microlejeunea). We tested alternative classification possibilities by conducting divergence time estimates based on DNA sequence variation of Lejeuneinae using the age of the fossil for corresponding age constraints. Consideration of the fossil as a stem group member of Microlejeunea or Lejeunea resulted in an Eocene to Late Cretaceous age of the Lejeuneinae crown group. This reconstruction is in good accordance with published divergence time estimates generated without the newly presented fossil evidence. Balancing available evidence, we describe the liverwort fossil as the extinct species Microlejeunea nyiahae, representing the oldest crown group fossil of Lejeuneaceae.
Homotherium was a genus of large-bodied scimitar-toothed cats, morphologically distinct from any extant felid species, that went extinct at the end of the Pleistocene [1-4]. They possessed large, saber-form serrated canine teeth, powerful forelimbs, a sloping back, and an enlarged optic bulb, all of which were key characteristics for predation on Pleistocene megafauna [5]. Previous mitochondrial DNA phylogenies suggested that it was a highly divergent sister lineage to all extant cat species [6-8]. However, mitochondrial phylogenies can be misled by hybridization [9], incomplete lineage sorting (ILS), or sex-biased dispersal patterns [10], which might be especially relevant for Homotherium since widespread mito-nuclear discrepancies have been uncovered in modern cats [10]. To examine the evolutionary history of Homotherium, we generated a ∼7x nuclear genome and a ∼38x exome from H. latidens using shotgun and target-capture sequencing approaches. Phylogenetic analyses reveal Homotherium as highly divergent (∼22.5 Ma) from living cat species, with no detectable signs of gene flow. Comparative genomic analyses found signatures of positive selection in several genes, including those involved in vision, cognitive function, and energy consumption, putatively consistent with diurnal activity, well-developed social behavior, and cursorial hunting [5]. Finally, we uncover relatively high levels of genetic diversity, suggesting that Homotherium may have been more abundant than the limited fossil record suggests [3, 4, 11-14]. Our findings complement and extend previous inferences from both the fossil record and initial molecular studies, enhancing our understanding of the evolution and ecology of this remarkable lineage.