A new statistical method for estimating divergence dates of species from DNA sequence data by a molecular clock approach is developed. This method takes into account effectively the information contained in a set of DNA sequence data. The molecular clock of mitochondrial DNA (mtDNA) was calibrated by setting the date of divergence between primates and ungulates at the Cretaceous-Tertiary boundary (65 million years ago), when the extinction of dinosaurs occurred. A generalized least-squares method was applied in fitting a model to mtDNA sequence data, and the clock gave dates of 92.3 +/- 11.7, 13.3 +/- 1.5, 10.9 +/- 1.2, 3.7 +/- 0.6, and 2.7 +/- 0.6 million years ago (where the second of each pair of numbers is the standard deviation) for the separation of mouse, gibbon, orangutan, gorilla, and chimpanzee, respectively, from the line leading to humans. Although there is some uncertainty in the clock, this dating may pose a problem for the widely believed hypothesis that the pipedal creature Australopithecus afarensis, which lived some 3.7 million years ago at Laetoli in Tanzania and at Hadar in Ethiopia, was ancestral to man and evolved after the human-ape splitting. Another likelier possibility is that mtDNA was transferred through hybridization between a proto-human and a proto-chimpanzee after the former had developed bipedalism.

Dating of the human-ape splitting by a molecular clock of mitochondrial DNA.

Border Gateway Protocol (BGP) is the protocol backing the core routing decisions on the Internet. It maintains a table of IP networks or 'prefixes' which designate network reachability among autonomous systems (AS). Point of concern in BGP is its lack of effective security measures which makes Internet vulnerable to different forms of attacks. Many solutions have been proposed till date to combat BGP security issues but not a single one is deployable in practical scenario. Any security proposal with optimal solution should offer adequate security functions, performance overhead and deployment cost. This paper critically analyzes the deployment issues of best three proposals considering trade-off between security functions and performance overhead.

Comparative analysis of

The revolution that wasn't: a new interpretation of the origin of modern human behavior.

Recombinant DNA technology provides evolutionary biologists with another tool for making phylogenetic inference through contrasts of restriction endounuclease cleavage site maps or DNA sequences between homologous DNA segments found in different groups. This paper is limited to the problem of making phylogenetic inference from restriction site maps. Several methods for making such inference have already been used or proposed (Avise et al., 1979a, 1979b;NeiandLi, 1979; Ferris et al., 1981), but all these methods depend upon the assumption that shared restriction sites reflect common evolutionary origins and are not the result of convergent evolution. Unfortunately, convergent evolution occurs with high probability for this type of data (Templeton, 1983). In addition, data from several different restriction enzymes are generally pooled in these analyses. Recently, Adams and Rothman (1982) have examined the distributions of cleavage sites and related sequences for 54 restriction endonucleases. They concluded 1) that cleavage sites and related sequences are distributed non-randomly in most DNA sequences, 2) that there is considerable heterogeneity between different restriction enzymes (even those with recognition sequences of the same length) with respect to the number and distribution of their respective cleavage sites and related sequences, and 3) that inference of phylogenetic relationship based on distances will be biased. In addition, Brown et al. (1982) sequenced 896 base pairs of the mitochondrial DNA from humans and apes and concluded that about 90% of the substitutions were transitions. The predominance of transitions over transversions increases the probability of convergence over that expected when all base substitutions are assumed to be equally likely (Templeton, 1983). Therefore, a need exists for an algorithm of phylogenetic inference that deals more directly with the problem of convergent evolution and statistical inhomogeneity between different restriction enzymes. In this paper, I propose such an algorithm. After discussing the problem of estimation of a phylogenetic tree, the task of statistical testing is then addressed. First, I present a non-parametric statistical framework for testing the fit of one hypothesized phylogeny versus an alternative phylogeny. Second, non-parametric statistical procedures are presented for testing hypotheses about relative rates of evolution among the various lineages.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1558-5646.1983.tb05533.x

Phylogenetic inference from restriction endonuclease cleavage site maps with particular reference to the evolution of humans and the apes.

The Brush Foundation studies on human growth and development, begun in 1931 and terminated in 1942, have been intensively reviewed and studied by Dr Greulich and Miss Pyle in the formulation of this Radiographic Atlas of Skeletal Development of the Hand and Wrist Serial radiographs of from 2 to 20 hand-films made at successive examinations of each of 1000 boys and girls made up the radiographic material Standards were selected that were judged to be the most representative of the central tendency or anatomic mode of each chronologic age group from birth through 18 years

Radiographic Atlas of Skeletal Development of the Hand and Wrist

The postcranial skeleton of Australopithecus afarensis from the Hadar Formation, Ethiopia, and the footprints from the Laetoli Beds of northern Tanzania, are analyzed with the goal of determining (1) the extent to which this ancient hominid practiced forms of locomotion other than terrestrial bipedality, and (2) whether or not the terrestrial bipedalism of A. afarensis was notably different from that of modern humans. It is demonstrated that A. afarensis possessed anatomic characteristics that indicate a significant adaptation for movement in the trees. Other structural features point to a mode of terrestrial bipedality that involved less extension at the hip and knee than occurs in modern humans, and only limited transfer of weight onto the medial part of the ball of the foot, but such conclusions remain more tentative than that asserting substantive arboreality. A comparison of the specimens representing smaller individuals, presumably female, to those of larger individuals, presumably male, suggests sexual differences in locomotor behavior linked to marked size dimorphism. The males were probably less arboreal and engaged more frequently in terrestrial bipedalism. In our opinion, A. afarensis from Hadar is very close to what can be called a "missing link." We speculate that earlier representatives of the A. afarensis lineage will present not a combination of arboreal and bipedal traits, but rather the anatomy of a generalized ape.

The locomotor anatomy of Australopithecus afarensis.

Numerous studies of the locomotor skeleton of the Hadar hominids have revealed traits indicative of both arboreal climbing/suspension and terrestrial bipedalism. These earliest known hominids must have devoted part of their activities to feeding, sleeping and/or predator avoidance in trees, while also spending time on the ground where they moved bipedally. In this paper we offer new data on phalangeal length and curvature, moφhology of the tarsus and metatarsophalangeal joints, and body proportions that further strengthen the argument for arboreality in the Hadar hominids. We also provide additional evidence on limb and pedal proportions and on the functional anatomy of the hip, knee and foot, indicating that the bipedality practiced at Hadar differed from that of modern humans. Consideration of the ecology at Hadar, in conjunction with modern primate models, supports the notion of arboreality in these earliest australopithecines. We speculate that selection for terrestrial bipedality may have intensified through the Plio-Pleistocene as forests and woodland patches shrunk and the need arose to move increasingly longer distances on the ground. Only with Homo erectus might body size, culture and other factors have combined to ‘release’ hominids from their dependence on trees.

Arboreality and bipedality in the Hadar hominids.

Comparisons of hominoid metacarpals and phalanges reveal differences, many of which are closely linked to locomotor hand postures. The African apes display features of the metacarpals and phalanges which distinguish them from the other Hominoidea. These features are most evident in digits III and IV. The orangutan hand is demonstrably less well adapted to knuckle-walking and is distinctive in its adaptation to power and hook grasping of vertical and horizontal supports, respectively. Orangutan fingers possess a "double-locking" mechanism (Napier, '60), and a slight ulnad shift in the axis of the hand which results in lengthened phalanges of ray IV. Hylobatid apes are more like orangutans in their finger morphology than any of the other Hominoidea, but exhibit unique features of their own. These include elongate phalanges of fingers II-V. Human metacarpals II-V form two sets composed of II-III, and IV-V. The heads of both metacarpals II and III are characterized by axial torsion. This reflects the enhanced manipulatory role of the third finger in humans. Human distal phalanges are unique in the development of pronounced apical tufts. Multivariate analysis of metacarpal III and proximal III yields variables that array the extant apes along an arboreal-terrestrial axis, from hylobatid apes to male gorillas. The positions of taxa on this discriminant concur with observations on the locomotion of free-ranging apes.

Comparative and functional morphology of hominoid fingers

Hominid evolution past, present and future

Although several Plio-Pleistocene hominids are found in association with stone and bone tools, it has been generally assumed that at any one time the hominid with the largest brain was the toolmaker. Fossils recovered over the last decade suggest that early hominids subsequent to 2.5 million years ago all might have used tools and occupied "cultural" niches. A test for humanlike precision grasping (the enhanced ability to manipulate tools) is proposed and applied to australopithecines and early Homo. The results indicate that tools were likely to have been used by all early hominids at around 2.0 million years ago. The earliest australopithecines, which predate the appearance of stone tools in the archaeological record, do not show signs of advanced precision grasping.

https://science.sciencemag.org/content/sci/265/5178/1570.full.pdf

Randall L. Susman

Papers

The locomotor anatomy of Australopithecus afarensis.

Arboreality and bipedality in the Hadar hominids.

Comparative and functional morphology of hominoid fingers

Hominid evolution past, present and future

Fossil Evidence for Early Hominid Tool Use