How We Got Here: Evolutionary Changes in Skull Shape in Humans & Their Ancestors

2012 ◽  
Vol 74 (2) ◽  
pp. 106-110 ◽  
Author(s):  
Rebecca M. Price
Keyword(s):  
Homo Sapiens ◽  
Homo Erectus ◽  
Australopithecus Afarensis ◽  
Skull Shape ◽  
Evolutionary Changes

This activity uses inquiry to investigate how large changes in shape can evolve from small changes in the timing of development. Students measure skull shape in fetal, infant, juvenile, and adult chimpanzees and compare them to adult skulls of Homo sapiens, Homo erectus, and Australopithecus afarensis. They conclude by re-interpreting their findings in light of Ardipithecus ramidus.

Plio-pleistocene Hominids: Epistemological and Taxonomic Problems

1970 ◽  
Vol 9 (1) ◽  
pp. 169-202
Author(s):  
Jolanta Koszteyn
Keyword(s):  
Homo Sapiens ◽  
Single Species ◽  
Homo Erectus ◽  
Australopithecus Afarensis ◽  
Homo Heidelbergensis ◽  
Genealogical Tree ◽  
Homo Neanderthalensis ◽  
Homo Habilis ◽  
Homo Antecessor ◽  
Historical Times

Within the historical times, which roughly corresponds with the Holocene epoch, the whole of mankind is believed to be a single species. Homo sapiens. But the human genealogical tree (phylogeny) is populated by a really astounding number of paleontological species and paleontological genera: Ardipithecus ramidus, Australopithecus anamensis, Australopithecus afarensis, Australopithecus africanus, Paranthropus robustus, Paranthropus boisei, Homo habilis, Homo georgicus. Homo erectus, Homo ergaster, Homo antecessor, Homo heidelbergensis, Homo neanderthalensis, Homo sapiens. (cf. Gyula 2002). In fact there are many more (Sahelanthropus tchadensis, Orrorin tugenensis, Kenyanthropus platyops, Australopithecus garhi, Australopithecus aethiopicus) but Foley (2002), quite reasonably, states that the evidence for their existence is, at present, insufficient. The existence of these multiple forms is beyond any doubt. The doubt, however arises concerning the human or „prehuman" status of them. Were they really true specific forms, half-way between the apes and Holocene man? Is it possible that they constitute a number of different ecotypes (or paleoraces) within the same natural species of Homo sapiens?

Hominin transition to Upper Pliocene

2017 ◽  
Author(s):  
Francisco J. Ayala ◽  
Camilo J. Cela-Conde
Keyword(s):  
Brain Development ◽  
Late Pleistocene ◽  
Technological Progress ◽  
Homo Sapiens ◽  
Middle Pleistocene ◽  
Evolutionary Significance ◽  
Australopithecus Afarensis ◽  
Phylogenetic Significance ◽  
Homo Neanderthalensis ◽  
Surprising Discovery

This chapter analyzes the transition of the hominins from the Middle Pleistocene to the Late Pleistocene. Two alternative models are explored, the “Multiregional Hypothesis” (MH) and the “Replacement Hypothesis,” and how each model evaluates the existing relationships between the taxa Homo neanderthalensis and Homo sapiens. Next is the investigation of the transitional (or “archaic,” if this grade is taken into account) exemplars found in Europe, Africa, and Asia and their evolutionary significance. In particular, the comparison between H. erectus and H. sapiens in China and Java is investigated, as the main foundation of the MH. The chapter ends with the surprising discovery of Homo floresiensis and its description and interpretations concerning its taxonomic and phylogenetic significance. The correlation between brain development and technological progress is at odds with the attribution of perforators, microblades, and fishing hooks to a hominin with a small cranial volume, similar to that of Australopithecus afarensis.

scholarly journals Recent origin of low trabecular bone density in modern humans

2014 ◽  
Vol 112 (2) ◽  
pp. 366-371 ◽  
Author(s):  
Habiba Chirchir ◽  
Tracy L. Kivell ◽  
Christopher B. Ruff ◽  
Jean-Jacques Hublin ◽  
Kristian J. Carlson ◽  
...  
Keyword(s):  
Body Size ◽  
Trabecular Bone ◽  
Homo Sapiens ◽  
Modern Human ◽  
Homo Erectus ◽  
Lower Limbs ◽  
Modern Humans ◽  
Human Skeleton ◽  
Trabecular Density ◽  
Fossil Hominins

Humans are unique, compared with our closest living relatives (chimpanzees) and early fossil hominins, in having an enlarged body size and lower limb joint surfaces in combination with a relatively gracile skeleton (i.e., lower bone mass for our body size). Some analyses have observed that in at least a few anatomical regions modern humans today appear to have relatively low trabecular density, but little is known about how that density varies throughout the human skeleton and across species or how and when the present trabecular patterns emerged over the course of human evolution. Here, we test the hypotheses that (i) recent modern humans have low trabecular density throughout the upper and lower limbs compared with other primate taxa and (ii) the reduction in trabecular density first occurred in early Homo erectus, consistent with the shift toward a modern human locomotor anatomy, or more recently in concert with diaphyseal gracilization in Holocene humans. We used peripheral quantitative CT and microtomography to measure trabecular bone of limb epiphyses (long bone articular ends) in modern humans and chimpanzees and in fossil hominins attributed to Australopithecus africanus, Paranthropus robustus/early Homo from Swartkrans, Homo neanderthalensis, and early Homo sapiens. Results show that only recent modern humans have low trabecular density throughout the limb joints. Extinct hominins, including pre-Holocene Homo sapiens, retain the high levels seen in nonhuman primates. Thus, the low trabecular density of the recent modern human skeleton evolved late in our evolutionary history, potentially resulting from increased sedentism and reliance on technological and cultural innovations.

scholarly journals Dental tissue proportions in fossil orangutans from mainland Asia and Indonesia

2011 ◽  
Vol 1 (1) ◽  
pp. e1 ◽  
Author(s):  
Tanya M. Smith ◽  
Anne-Marie Bacon ◽  
Fabrice Demeter ◽  
Ottmar Kullmer ◽  
Kim Thuy Nguyen ◽  
...  
Keyword(s):  
Fossil Record ◽  
Homo Sapiens ◽  
Homo Erectus ◽  
Dental Tissue ◽  
Developmental Constraints ◽  
Enamel Thickness ◽  
Selective Pressures ◽  
The Past ◽  
Geometric Scaling ◽  
Dental Reduction

Orangutans (Pongo) are the only great ape genus with a substantial Pleistocene and Holocene fossil record, demonstrating a much larger geographic range than extant populations. In addition to having an extensive fossil record, Pongo shows several convergent morphological similarities with Homo, including a trend of dental reduction during the past million years. While studies have documented variation in dental tissue proportions among species of Homo, little is known about variation in enamel thickness within fossil orangutans. Here we assess dental tissue proportions, including conventional enamel thickness indices, in a large sample of fossil orangutan postcanine teeth from mainland Asia and Indonesia. We find few differences between regions, except for significantly lower average enamel thickness (AET) values in Indonesian mandibular first molars. Differences between fossil and extant orangutans are more marked, with fossil Pongo showing higher AET in most postcanine teeth. These differences are significant for maxillary and mandibular first molars. Fossil orangutans show higher AET than extant Pongo due to greater enamel cap areas, which exceed increases in enamel-dentine junction length (due to geometric scaling of areas and lengths for the AET index calculation). We also find greater dentine areas in fossil orangutans, but relative enamel thickness indices do not differ between fossil and extant taxa. When changes in dental tissue proportions between fossil and extant orangutans are compared with fossil and recent Homo sapiens, Pongo appears to show isometric reduction in enamel and dentine, while crown reduction in H. sapiens appears to be due to preferential loss of dentine. Disparate selective pressures or developmental constraints may underlie these patterns. Finally, the finding of moderately thick molar enamel in fossil orangutans may represent an additional convergent dental similarity with Homo erectus, complicating attempts to distinguish these taxa in mixed Asian faunas. 

The Continuum of Psychosis and Its Genetic Origins

1990 ◽  
Vol 156 (6) ◽  
pp. 788-797 ◽  
Author(s):  
T. J. Crow
Keyword(s):  
Sex Chromosome ◽  
Homo Sapiens ◽  
Polymorphic Marker ◽  
Cerebral Dominance ◽  
Homo Erectus ◽  
Evolutionary Development ◽  
Pseudoautosomal Region ◽  
Sibling Pairs ◽  
Homo Habilis ◽  
Y Chromosomes

Attempts to draw a line of genetic demarcation between schizophrenic and affective illnesses have failed. It must be assumed that these diseases are genetically related. A post-mortem study has demonstrated that enlargement of the temporal horn of the lateral ventricle in schizophrenia but not in Alzheimer-type dementia is selective to the left side of the brain. This suggests that the gene for psychosis is the ‘cerebral dominance gene‘, the factor that determines the asymmetrical development of the human brain. That the psychosis gene is located in the pseudoautosomal region of the sex chromosomes is consistent with observations that sibling pairs with schizophrenia are more often than would be expected of the same sex and share alleles of a polymorphic marker at the short-arm telomeres of the X and Y chromosomes above chance expectation. That the cerebral dominance gene also is pseudoautosomal is suggested by the pattern of verbal and performance deficits associated with sex-chromosome aneuploidies. The psychoses may thus represent aberrations of a late evolutionary development underlying the recent and rapid increase in brain weight in the transition fromAustralopithecusthroughHomo habilisandHomo erectustoHomo sapiens.

scholarly journals Homoplasy in the evolution of modern human-like joint proportions in Australopithecus afarensis

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Anjali M Prabhat ◽  
Catherine K Miller ◽  
Thomas Cody Prang ◽  
Jeffrey Spear ◽  
Scott A Williams ◽  
...  
Keyword(s):  
Upper Limb ◽  
Lower Limb ◽  
Modern Human ◽  
Homo Erectus ◽  
Australopithecus Afarensis ◽  
Modern Humans ◽  
Homo Habilis ◽  
Hominin Evolution ◽  
Parsimonious Explanation ◽  
Phylogenetic Hypotheses

The evolution of bipedalism and reduced reliance on arboreality in hominins resulted in larger lower limb joints relative to the joints of the upper limb. The pattern and timing of this transition, however, remains unresolved. Here, we find the limb joint proportions of Australopithecus afarensis, Homo erectus, and Homo naledi to resemble those of modern humans, whereas those of A. africanus, Australopithecus sediba, Paranthropus robustus, Paranthropus boisei, Homo habilis, and Homo floresiensis are more ape-like. The homology of limb joint proportions in A. afarensis and modern humans can only be explained by a series of evolutionary reversals irrespective of differing phylogenetic hypotheses. Thus, the independent evolution of modern human-like limb joint proportions in A. afarensis is a more parsimonious explanation. Overall, these results support an emerging perspective in hominin paleobiology that A. afarensis was the most terrestrially adapted australopith despite the importance of arboreality throughout much of early hominin evolution.

scholarly journals Human mitochondrial DNA diversity is compatible with the multiregional continuity theory of the origin of Homo sapiens

2021 ◽  
Vol 84 (4) ◽  
pp. 487-502
Author(s):  
Robert B. Eckhardt
Keyword(s):  
Homo Sapiens ◽  
Sequence Divergence ◽  
Homo Erectus ◽  
Gradual Transition ◽  
Complete Replacement ◽  
Human Mitochondrial Dna ◽  
Coalescence Time ◽  
Dna Diversity ◽  
Mtdna Sequence ◽  
Out Of Africa

Abstract Confidence intervals for estimates of human mtDNA sequence diversity, chimpanzee-human mtDNA sequence divergence, and the time of splitting of the pongid-hominid lineages are presented. Consistent with all the data used in estimating the coalescence time for human mitochondrial lineages to a common ancestral mitochondrion is a range of dates from less than 79,000 years ago to more than 1,139,000 years ago. Consequently, the hypothesis that a migration of modern humans (Homo sapiens) out of Africa in the range of 140,000 to 280,000 years ago resulted in the complete replacement, without genetic interchange, of earlier Eurasian hominid populations (Homo erectus) is but one of several possible interpretations of the mtDNA data. The data are also compatible with the hypothesis, suggested earlier and supported by fossil evidence, of a single, more ancient expansion of the range of Homo erectus from Africa, followed by a gradual transition to Homo sapiens in Europe, Asia, and Africa.

scholarly journals Arguments that Prehistorical and Modern Humans Belong to the Same Species

2019 ◽  
Author(s):  
Rainer Kühne
Keyword(s):  
Homo Sapiens ◽  
Single Species ◽  
Homo Erectus ◽  
Modern Humans ◽  
Homo Neanderthalensis ◽  
Out Of Africa

I argue that the evidence of the Out-of-Africa hypothesis and the evidence of multiregional evolution of prehistorical humans can be understood if there has been interbreeding between Homo erectus, Homo neanderthalensis, and Homo sapiens at least during the preceding 700,000 years. These interbreedings require descendants who are capable of reproduction and therefore parents who belong to the same species. I suggest that a number of prehistorical humans who are at present regarded as belonging to different species belong in fact to one single species.  

Birth and Death of the Holocene

2012 ◽  
Author(s):  
Jan Zalasiewicz ◽  
Mark Williams
Keyword(s):  
Homo Sapiens ◽  
Homo Erectus ◽  
Quaternary Period ◽  
Climate Oscillations ◽  
The Holocene ◽  
Homo Neanderthalensis ◽  
Droughts And Floods ◽  
Major Shift ◽  
Place Of Origin ◽  
The Many

It is just the latest of many climate phases of the Quaternary Period. The 103rd major shift in climate-driven global oxygen isotope values, to be precise, since the official-designated beginning of the Quaternary Period, 2.58 million years ago. And, many of those major phases, as we have seen, include dozens of climate oscillations far greater in scale than humans have witnessed since written records began. Nevertheless, it is our warm phase, that within which our civilization has grown, and hence it has been separated as a distinct epoch, the Holocene, a little over 0.01 of a million years long. Its counterpart is the Pleistocene Epoch, in which reside those other 2.57 million years of Quaternary time, and those other 102 major climate oscillations. Thus, we live—at least as far as formal geological nomenclature goes—in a privileged time. When this epoch began, Homo sapiens had already existed for some 150,000 years. As a species its prospects might not have seemed bright: this creature lacked anything terribly impressive in the way of claws or teeth or thick fur or armour. But by being ingenious at developing what one might describe as artificial claws and teeth—axes and spears and arrows—it could kill and eat mammals considerably larger than itself. In those early days, it might not have prospered, exactly, but it clung to existence, seemingly weathering at least one very bad patch, several tens of thousands of years ago, when its numbers dropped almost to extinction levels. It survived the climate oscillations of the late Pleistocene—the droughts and floods and episodes of bitter cold and killing heat—by adapting its behaviour or migrating as best it could. Its migrations from its place of origin, Africa, were on an epic scale. The many thousands of individual and collective stories of hope, fear, endurance, courage, tragedy, and (less commonly) triumph are all lost. What remains is the evidence that humans, by the beginning of the Holocene, had spread widely over Europe and Asia, ousting (it seems) their kindred hominin species, Homo neanderthalensis and Homo erectus.

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