Brain expansion compounding the hominid heritage
The million year timespan often assumed for the emergence of Homo habilis from smaller-brained hominids seems brief, when considered in the abstract. But even seemingly short spans of time allow for the compounding of gains, even if each increment is so slight as to be scarcely noticeable in itself. What Einstein, like Darwin, saw in compounding - the physicist, because of his mathematical mind, explicitly, the naturalist perhaps intuitively - was the vast power of cumulative growth. A...
Ferment in physics
As has already proved to be the case with modern physics, structures of thought that have served well in the past can become so constraining that they impede further progress until they are modified sharply or even discarded. At the end of the nineteenth century, the British physicist Lord Kelvin is said to have advised his best students to avoid careers in physics because all of the interesting work had been done. So typical was this attitude that it was echoed in Albert A. Michelson's 1905...
Developmental perspectives on postcranial evolution
Contrasting views on the tempo and mode of evolution among early hominids were brought into sharp focus by the discovery and interpretation of OH 62 from lower Bed I at Olduvai Gorge, dated indirectly to about 1.8 Ma Johanson et al., 1987 . The OH 62 skeletal material came from a scrappy surface find that comprised a total of nearly 18 000 separate fragments of bones and teeth from a variety of different animals ranging from fish through giraffes. The numerous hominid elements were...
Time and change undermine taxonomic categorization
As we have seen, taxonomy, at least in the European tradition, had started with Plato's conception of an abstract ideal of the species. His concept of our perception of real organisms as imperfect, flickering shadows on the wall of a cave, mere reflections of an abstract and more perfect reality, was nurtured from antiquity, through the Middle Ages and the Renaissance. This vision was later multiplied by Linnaeus into thousands of taxa that were for the most part discrete, plus a very few...
Pithecanthropines
At this point in the expansion of the hominid paleontological record the pattern changes, with the fossil evidence beginning to attract enough attention that anticipation was even running a bit ahead of the evidence. For instance, in his work The Evolution of Man, the German naturalist Ernst Haeckel 1879 went so far as to coin a name, Pithecanthropus alalus, for a fossil yet to be discovered. As events developed, however, he didn't have to wait long for his expectations to be realized. Inspired...
Mendel and particulate inheritance
Entirely unknown to Charles Darwin, a mechanism that could explain conservation of variation in the face of selection, and without blending or dilution, already had been supplied by Gregor Mendel 1822-1884 , an Augustinian monk who lived in Brn, Austria now Brno in the Czech Republic . Mendel's name and the general nature of his scientific contributions are widely familiar. Although many people today are aware of Mendel's fame, few appreciate fully the nature of his work or its significance....
The adaptive capacities of chimpanzees
Evidence for short-term adaptation among chimpanzees Among extant humans, enamel hypoplasias record certain life history events of brief duration. Corresponding records of stress have been known to mark the teeth of various nonhuman primates, including chimpanzees, since the observations recorded by Colyer 1936 . Limited data on freeranging chimpanzees also were provided by Jones amp Cave 1960 , who found transverse enamel hypoplasias in over 46 percent of 13 specimens sampled in Sierra Leone....
A papionine perspective on hominid paleobiology
The populations of terrestrial and semi-terrestrial monkeys that were surveyed in Chapter 6 are amenable to study along the lines discussed by Foley 1987, 1995 and outlined earlier in this chapter. As a group, the macaques, baboons, and their other near relatives constitute a natural experiment, allowing for an interplay of observation and hypothesis testing. Among the papionines, phenostructure and zygostructure do not coincide, with the result that phylogenetic inferences based on...
Temporal distribution of chimpanzee populations
Chimpanzees have virtually no paleontological record, at least in the sense of fossilized skeletal parts that would be anatomically duplicated in detail by those of extant Pan species. In a broader view, however, there are abundant fossil remains of medium to large bodied hominoids preserved in geological deposits of Africa for about 20 million years, with what appear to be moderately later expansions into Europe. Although dozens of binomials have been applied to various specimens, these...
Large gene effects or small Mendelians vs biometricians
Far from facilitating the acceptance of natural selection by removing the problem posed by blending inheritance, the rediscovery of Mendel's laws actually retarded the acceptance of Darwin's theory by calling into ques tion the outcome of selection acting on small continuous variations. Ammunition was thereby given to partisans of large discontinuous phenotypic effects then referred to as 'sports' - or so the Mendelians thought Provine, 1971 . Because the interchange of viewpoints involved some...
Phenotypic features of chimpanzees
Chimpanzees are moderately large mammals with long trunks and chests that are deep and broadened laterally compared to quadrupedal primates. Like all extant hominoids, they lack an external tail. Their forelimbs are much longer than their hindlimbs. Chimpanzee feet exhibit great toes that are deeply divided from the others and sufficiently opposable to be used for grasping, in addition to hands that, despite their short thumbs, are suited for manipulation as well as prehension. On the middle...
Limitations of the evidence
The sites summarized above are distributed geographically in Africa along an axis that extends from Ethiopia, through the Great Rift Valley of East Africa, down nearly to the southern tip of the continent. Temporally the strata from which the hominid remains have been recovered range from more than five million years ago to about a million years before the present, for a total timespan of about four million years. It is difficult to give the exact number of individual hominids known from this...
Hominid antecedents the Eurafrican hominoid fossil record
The accumulating molecular evidence establishes Africa as the central focus for intensive scrutiny of fossil material around the time of transition. Recent developments in paleogeographic studies widen this spatial horizon somewhat, since for significant parts of the later Tertiary period, Africa and Europe were united in a single province which was separated from much of Asia by the climatic shift that dried up the Mediterranean Sea. The fossil record for hominoid evolution in the Eurafrican...
The adaptive capacities of papionine primates
As already noted, papionine primates are widely distributed across Africa and Eurasia, often overlapping extensively with human populations. Consequently, they have been widely observed under field conditions in the wild, in monkey centers that may be either semi-naturalistic or widely different from original locations and habitats for example, macaques have lived for several decades on Cayo Santiago near Puerto Rico , and in the artificial settings that exist in laboratories. The resultant...
Taxonomy as a conceptual framework
Naming objects and arranging them into categories is a fundamental and universal aspect of human mental activity. Some of the specific forms of names for organisms, and the systems used to frame discussions of relationships among populations represented by human fossils as well as all other things now or once alive , trace back at least to the time of ancient Greek civilization. An identifiable early figure who shaped this line of thought was Plato 429-347 BCE - Before the Christian Era , a...