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PubMed1985

Characterization of 4,4'-Diisothiocyano-2,2'-disulfonic Acid Stilbene Inhibition of 3-Phosphoglycerate-Dependent O(2) Evolution in Isolated Chloroplasts : Evidence for a Common Binding Site on the C(4) Phosphate Translocator for 3-Phosphoglycerate, Phosphoenolpyruvate, and Inorganic Phosphate.

3-Phosphoglycerate (PGA)-dependent O(2) evolution by mesophyll chloroplasts of the C(4) plant, Digitaria sanguinalis L. Scop. (crabgrass), was inhibited by micromolar levels of 4,4'-diisothiocyano-2,2'-disulfonic acid stilbene (DIDS). As little as 1.8 micromolar DIDS added to the assay medium (containing 0.7 millimolar PGA) resulted in 80 to 100% inhibition of O(2) evolution. The extent of inhibition of O(2) evolution observed was dependent on various factors including: pH, concentration of DIDS to relative chlorophyll, concentration of PGA, and the time of addition of DIDS to the chloroplasts relative to addition of PGA.Preincubation of crabgrass chloroplasts with micromolar levels of DIDS, followed by washing to remove any nonirreversibly bound DIDS, inhibited PGA-dependent O(2) evolution. Protection against this inhibition was afforded by preincubating the chloroplasts with various substrates before adding DIDS. For example, if the chloroplasts were first incubated with 8.3 millimolar PGA, phosphoenolpyruvate (PEP) or inorganic phosphate before adding 42 micromolar DIDS, the percentage of inhibition was decreased from 100% (without any substrate) to 0, 54, and 67%, respectively. 2-Phosphoglycerate caused a slight decrease in the inhibition (about 10%) and glucose-6-phosphate had no protective effect. If the chloroplasts were pretreated with DIDS initially, the inhibition could not be overcome by PGA, suggesting that DIDS acts as an irreversible inhibitor. Micromolar levels of DIDS also inhibited PGA dependent O(2) evolution by isolated chloroplasts of the C(3) plant barley. As with crabgrass, preincubation with PGA or inorganic phosphate resulted in a decrease in the DIDS inhibition, but PEP was very ineffective compared to the C(4) chloroplasts.Oxalacetate-dependent O(2) evolution and its stimulation by the uncoupler, NH(4)Cl, were unaffected by the addition of DIDS to crabgrass mesophyll chloroplasts. Furthermore, preincubation of the chloroplasts with DIDS (up to 65 micromolar) had no inhibitory effect on the extractable activity of NADP glyceraldehyde-3-P dehydrogenase and phosphoglycerate kinase. Inhibition by DIDS was interpreted to be at the substrate binding site of the phosphate translocator. The data further suggest that in C(4) crabgrass chloroplasts, PEP is transported on a carrier which also transports PGA.

Journal Article↗

PubMed1986

The Relationship between H(2) Evolution and Acetylene Reduction in Pisum sativum-Rhizobium leguminosarum Symbioses Differing in Uptake Hydrogenase Activity.

Peas (Pisum sativum L.) were inoculated with strains of Rhizobium leguminosarum having different levels of uptake hydrogenase (Hup) activity and were grown in sterile Leonard jars under controlled conditions. Rates of H(2) evolution and acetylene reduction were determined for intact nodulated roots at intervals after the onset of darkness or after removal of the shoots. Hup activity was estimated using treatment plants or equivalent plants from the growth chamber, by measuring the uptake of H(2) or (3)H(2) in the presence of acetylene. In all cases, the rate of H(2) evolution was a continuous function of the rate of acetylene reduction. In symbioses with no demonstrable Hup activity, H(2) evolution increased in direct proportion to acetylene reduction and the slopes were similar with the Hup(-) strains NA502 and 128C79. Hup activity was similar in strains 128C30 and 128C52 but significantly lower in strain 128C54. With these strains, the slopes of the H(2) evolution versus acetylene reduction curves initially increased with acetylene reduction, but became constant and similar to those for the Hup(-) strains at high rates of acetylene reduction. On these parallel portions of the curves, the decreases in H(2) evolution by Hup(+) strains were similar in magnitude to their H(2)-saturated rates of Hup activity. The curvilinear relationship between H(2) evolution and acetylene reduction for a representative Hup(+) strain (128C52) was the same, regardless of the experimental conditions used to vary the nitrogenase activity.

Journal Article↗

PubMed1998

Changes in matrix metalloproteinases during the evolution of interstitial renal fibrosis in a rat experimental model.

The aim of the present study was to analyze the matrix metalloproteinase (MMP) activity during the evolution of interstitial renal fibrosis in a rat experimental model of unilateral ureteral obstruction. The interstitial type I collagenase and the gelatinolytic activities were analyzed by radiolabeled substrate degradation. Interstitial collagenase activity was low at all times while gelatinolytic activity increased on day 6 of evolution, with a decrease in activity from this point. The use of organomercurials revealed the presence of latent enzyme in all cases. Normal kidney samples contained MMP-9 in both active and proenzyme forms as revealed by zymography. On day 3 MMP-9 dimers appeared, and increased activity was observed until day 6. A decrease in the gelatinolytic activity was detected from days 9-15 of evolution. This observation was confirmed by Western blot analysis that revealed the presence of proMMP-9 mainly from days 6-12. Tissue inhibitor of metalloproteinase-1 (TIMP-1) was also detected alone and in combination with proMMP-1 and MMP-1, particularly from days 6-15 of evolution. The presence of MMP-9 and MMP-1 was detected in the cytoplasm of cortical tubular cells by immunohistochemistry, with no difference between the experimental and the normal kidneys. There was also an increase in collagen concentration from day 3 after surgery that increased during the entire evolution of the experimental model. This work reveals that the decrease in the MMP-9 and MMP-1 enzymatic activity, due to their interaction with TIMP-1 and to the lack of activation of the latent forms, may participate in the excessive collagen deposit during the evolution of experimental interstitial renal fibrosis.

Animals↗

PubMed2006

Genome increase as a clock for the origin and evolution of life.

BACKGROUND: The size of non-redundant functional genome can be an indicator of biological complexity of living organisms. Several positive feedback mechanisms including gene cooperation and duplication with subsequent specialization may result in the exponential growth of biological complexity in macro-evolution. RESULTS: I propose a hypothesis that biological complexity increased exponentially during evolution. Regression of the logarithm of functional non-redundant genome size versus time of origin in major groups of organisms showed a 7.8-fold increase per 1 billion years, and hence the increase of complexity can be viewed as a clock of macro-evolution. A strong version of the exponential hypothesis is that the rate of complexity increase in early (pre-prokaryotic) evolution of life was at most the same (or even slower) than observed in the evolution of prokaryotes and eukaryotes. CONCLUSION: The increase of functional non-redundant genome size in macro-evolution was consistent with the exponential hypothesis. If the strong exponential hypothesis is true, then the origin of life should be dated 10 billion years ago. Thus, the possibility of panspermia as a source of life on earth should be discussed on equal basis with alternative hypotheses of de-novo life origin. Panspermia may be proven if bacteria similar to terrestrial ones are found on other planets or satellites in the solar system. REVIEWERS: This article was reviewed by Eugene V. Koonin, Chris Adami and Arcady Mushegian.

Journal Article↗

PubMed2006

A system for studying evolution of life-like virtual organisms.

BACKGROUND: Fitness landscapes, the dependences of fitness on the genotype, are of critical importance for the evolution of living beings. Unfortunately, fitness landscapes that are relevant to the evolution of complex biological functions are very poorly known. As a result, the existing theory of evolution is mostly based on postulated fitness landscapes, which diminishes its usefulness. Attempts to deduce fitness landscapes from models of actual biological processes led, so far, to only limited success. RESULTS: We present a model system for studying the evolution of biological function, which makes it possible to attribute fitness to genotypes in a natural way. The system mimics a very simple cell and takes into account the basic properties of gene regulation and enzyme kinetics. A virtual cell contains only two small molecules, an organic nutrient A and an energy carrier X, and proteins of five types--two transcription factors, two enzymes, and a membrane transporter. The metabolism of the cell consists of importing A from the environment and utilizing it in order to produce X and an unspecified end product. The genome may carry an arbitrary number of genes, each one encoding a protein of one of the five types. Both major mutations that affect whole genes and minor mutations that affect individual characteristics of genes are possible. Fitness is determined by the ability of the cell to maintain homeostasis when its environment changes. The system has been implemented as a computer program, and several numerical experiments have been performed on it. Evolution of the virtual cells usually involves a rapid initial increase of fitness, which eventually slows down, until a fitness plateau is reached. The origin of a wide variety of genetic networks is routinely observed in independent experiments performed under the same conditions. These networks can have different, including very high, levels of complexity and often include large numbers of non-essential genes. CONCLUSION: The described system displays a rich repertoire of biologically sensible behaviors and, thus, can be useful for investigating a number of unresolved issues in evolutionary biology, including evolution of complexity, modularity and redundancy, as well as for studying the general properties of genotype-to-fitness maps. REVIEWERS: This article was reviewed by Drs. Eugene Koonin, Shamil Sunyaev and Arcady Mushegian.

Journal Article↗

PubMed2006

Prospective evaluation of clonal evolution during long-term follow-up of patients with untreated early-stage chronic lymphocytic leukemia.

PURPOSE: Retrospective studies suggest cytogenetic abnormalities detected by interphase fluorescent in situ hybridization (FISH) can identify patients with chronic lymphocytic leukemia (CLL) who will experience a more aggressive disease course. Other studies suggest that patients may acquire chromosome abnormalities during the course of their disease. There are minimal prospective data on the clinical utility of the widely used hierarchical FISH prognostic categories in patients with newly diagnosed early-stage CLL or the frequency of clonal evolution as determined by interphase FISH. PATIENTS AND METHODS: Between 1994 and 2002, we enrolled 159 patients with previously untreated CLL (83% Rai stage 0/I) on a prospective trial evaluating clonal evolution by FISH. Patients provided baseline and follow-up specimens for FISH testing during 2 to 12 years. RESULTS: Chromosomal abnormalities detected by FISH at study entry predicted overall survival. Eighteen patients experienced clonal evolution during follow-up. The rate of clonal evolution increased with duration of follow-up with only one occurrence in the first 2 years (n = 71; 1.4%) but 17 occurrences (n = 63; 27%) among patients tested after 5+ years. Clonal evolution occurred among 10% of ZAP-70-negative and 42% of ZAP-70-positive patients at 5+ years (P = .008). CONCLUSION: This clinical trial confirms prospectively that cytogenetic abnormalities detected by FISH can predict overall survival for CLL patients at the time of diagnosis, but also suggests that many patients acquire new abnormalities during the course of their disease. Patients with higher ZAP-70 expression may be more likely to experience such clonal evolution. These findings have important implications for both clinical management and trials of early treatment for patients with high-risk, early-stage CLL.

Adult↗

PubMed2005

[The influence of the parasitemia on the evolution of the chronic Chagas' disease].

During 13 years, 190 individuals with chagasic infection were submitted to clinical and parasitological examinations to investigate the relationship between parasitemia and the evolution of chronic chagasic infection. Fifty-six patients with positive xenodiagnosis and 134 with negative exams were compared from 1988 to 91, it was found that 22 (39.3%) and 50 (37.3%), respectively, presented disease progression. The parasitemia was stratified into high, medium and low and the relation with the disease evolution showed that 5 (62.5%), 10 (41.7%) and 57 (36.1%), respectively, presented progressive disease, though without a statistically significant difference (p>0.05). When 20 patients with persistent parasitemia in 1976/91, were compared with 59 with negative xenodiagnosis, a progressive evolution was observed in 6 (30%) and 17 (28.8%), respectively. Comparing six patients with high parasitemia and 59 with negative exams, it was verified that 3 (50%) and 17 (28.8%), respectively, showed progressive disease, but this was not statistically significant, (p>0.05). Mean age with high, medium and low parasitemia were 39.6, 45.3 and 41.5 years, respectively, (p>0.05). Mean age in patients showing progressive, unaltered and regressive evolution was 46.4, 39.8 and 32.6 years, respectively, with a statistically significant difference between progressive and regressive evolution (p<0.05). It is suggested that high parasitemia did not have an influence on the evolution of the chronic infection.

Adolescent↗

PubMed2005

Believers and disbelievers in evolution.

BACKGROUND: Citizens of the United States are less likely than are citizens of Europe and several non-European nations to believe that humans evolved from an earlier species. Several theories have been proposed to explain Americans' disbelief in human evolution, but empirical investigation has been sparse. METHODS: Data on belief in evolution, on scientific knowledge unrelated to evolution, on socioeconomic status, on Christian religiosity, and on political polarity were identified in the General Social Surveys (GSSs) for 1993, 1994, and 2000. These data were then analyzed in bivariate and multivariate tests of theories about evolutionary and anti-evolutionary views. FINDINGS: Christian religiosity was the strongest correlate of disbelief in evolution. Low educational attainment was another positive, but weaker, correlate, though disbelief in evolution was not related to general measures of scientific knowledge. Political liberalism and political conservatism predicted evolutionary belief even after controlling for religiosity, education, and other potential confounders. Subcultural differences in belief -- those between blacks and whites, rural dwellers and urban dwellers, Southerners and non-Southerners, dogmatists and non-dogmatists -- became insignificant under appropriate controls. CONCLUSION: Christian religiosity, especially in a fundamentalist variety, was the primary correlate of disbelief in evolution. Lack of education was an important but lesser factor. Independent of religiosity and education, political conservatism predicted disbelief.

Journal Article↗

PubMed2002

Evolution of 3D deformities in adolescents with progressive idiopathic scoliosis.

The objective of this study was to conduct an intrasubject longitudinal study quantifying the evolution of two- and three-dimensional geometrical scoliotic descriptors. The evolution of regional and local scoliotic descriptors was analyzed between two scoliotic visits on a cohort of 28 adolescents with progressive idiopathic scoliosis. Mean age at the first visit was 12.7 +/- 1.7 years old and averaged time interval between two assessments reached 22.8 +/- 10.8 months. Scoliotic descriptors were obtained from three-dimensionally reconstructed spines. The initial thoracic Cobb angle was on average 35.3 degrees +/- 8.4 degrees (range, 14 degrees-54 degrees). The evolution of spinal curvatures and vertebral deformities was assessed statistically in terms of descriptor absolute variations, and of descriptor variations normalized with respect to time and to the increase in Cobb angle. At the thoracic level, vertebral wedging increased with curve severity in a relatively consistent pattern for most scoliotic patients and axial rotation mainly increased towards curve convexity with scoliosis severity. No consistent evolution was associated with the angular orientation of the maximum wedging. Thoracic kyphosis changes (increase and decrease) were observed in important proportions. Results of this study challenge the existence of a typical scoliotic evolution pattern and suggest that the scoliotic evolution is quite variable and patient-specific.

Adolescent↗

PubMedDate not supplied

Evolution of nutritional therapy prescription in critically ill patients.

AIM: The aim of this study was to investigate factors that may affect the evolution of the caloric prescription in critically ill patients. Local: Intensive care unit patients. PATIENTS: 60 patients (33 M and 27 F); median age = 49 (1593) y were followed prospectively. They were divided in three groups according to the diagnostic: (a) trauma (n=20); (b) surgical (n=22), and 3) medical treatment (n=18). Forty-and-one (68.3%) patients received enteral nutrition (EN), 17 (28.3%) parenteral nutrition (TPN), and 2 (3.4%) TNP and EN. Nutritional status was graded B or C by global subjective evaluation. METHODS: Endpoints of the study were the time to begin the nutritional support, success or failure of the caloric prescription, and the evolution of the planned caloric prescription. The caloric evolution was considered as success if the prescription for the patient attained: (a) 25% of the caloric requirements on the 1st day; (b) 50% until the 3rd day; (c) 75% until the 6th day; and (e) 100% until the 10th day of the beginning of the support. RESULTS: In 54 (90%) patients, the nutritional support has begun until 48 h after admission and in 73.3% (44 patients), until the first 24 hours. EN was most prescribed for both trauma and medical patients while NPT was most used for surgical patients (p < 0.01). Success in caloric prescription was obtained in 73.3% (44) of the patients. There was no statistical difference for the success on the evolution of the prescription related to sex, age, diagnostic group, albumin level, type of support, mortality, use of fiber or glutamine. Success was attained earlier in patients without (median = 3.8 [95% CI, 5.7-16.7] days) than with (11.2 [95% CI, 5.7-16.7] days; p < 0.01) mechanical ventilation. CONCLUSIONS: Early nutritional support and success on the evolution of the caloric prescription can be accomplished in most critically ill patients. Evolution of the caloric prescription was slower in mechanical ventilated patients.

Adolescent↗

PubMed1981

[Histologic evolution of acute alcoholic hepatitis].

Although acute alcoholic hepatitis is a frequent disease with distinct histologic diagnosis, the prognostic factors of its evolution are largely unknown. The present report analyzes the data of 18 patients with acute alcoholic liver disease submitted to two liver biopsies with a mean interval of 35 months. The results demonstrate a favorable histologic evolution in six of seven patients that abandoned alcohol ingestion, and an evolution to chronic liver disease in the remaining case. Out of six patients with continuous alcohol ingestion the evolution was unfavorable in five, while one case evolved to healing. Centrilobular fibrosis disappeared in the six cases that discontinued alcohol ingestion and who had favorable evolution, and it persisted in four of the six patients that continued drinking. The results suggest that centrilobular fibrosis is not always an unfavorable prognostic marker, and that the evolution of acute alcoholic hepatitis is not exclusively dependent on the continuation of alcohol abuse.

Acute Disease↗

PubMed1993

Discrimination between chilling-sensitive and chilling-resistant plants based on measurements of free fatty acid accumulation and inactivation of oxygen evolution in aged chloroplasts.

The effect of aging of isolated chloroplasts of two chilling-sensitive (CS) and three chilling-resistant (CR) plants on the inactivation of oxygen evolution and accumulation of free fatty acids (FFA) was studied at 30 degrees C, pH 5.5 or 7.0, in the absence or presence of either sorbitol or NaCl. Considerable accumulation of FFA in aged chloroplasts of CS plants: bean and maize line F7-RpIII was accompanied by a marked inactivation of oxygen evolution. This relation was not, however, found in chloroplasts of CR species: pea, wheat and maize line EP1-RpI, in which the accumulation of FFA upon aging was very low whereas the decline of the rate of oxygen evolution was pronounced. In contrast to changes observed at pH 5.5, the inactivation of oxygen evolution in chloroplasts of CR species aged at pH 7.0 was dependent on the composition of the medium, especially in wheat chloroplasts. Thus, for the evaluation of chilling sensitivity based on the measurements of oxygen evolution activity solely, either aging of chloroplasts at pH 5.5 or possibly at pH 7.0 with NaCl included into the incubation medium may be recommended. It is concluded that determination of both the extent of FFA accumulation and inactivation of oxygen evolution in aged chloroplasts might be applied as chilling tolerance indexes.

Chloroplasts↗

PubMed1997

Molecular complementarity I: the complementarity theory of the origin and evolution of life.

We assert that molecular complementarity is much more widespread than is commonly acknowledged in biological systems, if not actually ubiquitous. It creates the coupling necessary for non-equilibrium systems to form. It stabilizes aggregates against degradation, thereby increasing concentrations to levels adequate to foster the formation of prebiotic systems and represents the earliest form in which natural selection was manifested. Complementarity confers on all interacting parts of such systems in formation carrying capacity. RNA or DNA are not, therefore, necessary to the emergence of life, but represent specialized forms of complementary molecules adapted specifically to information storage and transmission. Non-genetic information exists in metabolic functions and probably preceded genetic information historically. Complementarity also provides the basis for homeostasis and buffering of such systems not only in a chemical, but also in structural and temporal terms. It provides a mechanism for understanding how new, emergent properties can arise, and a basis for the self-organization of systems. We demonstrate that such aggregates can have properties not predictable from their individual components, thus providing a means for understanding how new functions emerge during evolution. Selection is for modules rather than individual components. The formation of functional sub-systems that can then be integrated as modules greatly increases the probability of the emergence of life. The result of such modular evolution alters the standard view of evolution from a tree or bush-like image to an integrated network composed of alternating periods of integration (as molecules and molecular aggregates merge) and divergence (as molecules and aggregates undergo variations). This provides a mechanism for evolution by punctuated equilibria. Molecular complementarity puts strict limits on variations, however, preventing evolution from being random. The evolutionary, physiological and embryological consequences of this view of life are outlined, and various models and experiments described that further characterize it.

Animals↗

PubMed2001

Predicting the emergence of antibiotic resistance by directed evolution and structural analysis.

Directed evolution can be a powerful tool to predict antibiotic resistance. Resistance involves the accumulation of mutations beneficial to the pathogen while maintaining residue interactions and core packing that are critical for preserving function. The constraint of maintaining stability, while increasing activity, drastically reduces the number of possible mutational combination pathways. To test this theory, TEM-1 beta-lactamase was evolved using a hypermutator E. coli-based directed evolution technique with cefotaxime selection. The selected mutants were compared to two previous directed evolution studies and a database of clinical isolates. In all cases, evolution resulted in the generation of the E104K/M182T/G238S combination of mutations ( approximately 500-fold increased resistance), which is equivalent to clinical isolate TEM-52. The structure of TEM-52 was determined to 2.4 A. G238S widens access to the active site by 2.8 A whereas E104K stabilizes the reorganized topology. The M182T mutation is located 17 A from the active site and appears to be a global suppressor mutation that acts to stabilize the new enzyme structure. Our results demonstrate that directed evolution coupled with structural analysis can be used to predict future mutations that lead to increased antibiotic resistance.

Amino Acid Sequence↗

PubMed2005

"Winner takes it all": strongest node rule for evolution of scale-free networks.

We study a model for evolution of complex networks. We introduce information filtering for reduction of the number of available nodes to a randomly chosen sample, as a stochastic component of evolution. New nodes are attached to the nodes that have maximal degree in the sample. This is a deterministic component of network evolution process. This fact is unusual for evolution of scale-free networks and depicts a possible route for modeling network growth. We present both simulations and theoretical results for network evolution. The obtained degree distributions exhibit an obvious power-law behavior in the middle with the exponential cut off in the end. This highlights the essential characteristics of information filtering in the network growth mechanisms.

Algorithms↗

PubMed2006

Tracing the origin of functional and conserved domains in the human proteome: implications for protein evolution at the modular level.

BACKGROUND: The functional repertoire of the human proteome is an incremental collection of functions accomplished by protein domains evolved along the Homo sapiens lineage. Therefore, knowledge on the origin of these functionalities provides a better understanding of the domain and protein evolution in human. The lack of proper comprehension about such origin has impelled us to study the evolutionary origin of human proteome in a unique way as detailed in this study. RESULTS: This study reports a unique approach for understanding the evolution of human proteome by tracing the origin of its constituting domains hierarchically, along the Homo sapiens lineage. The uniqueness of this method lies in subtractive searching of functional and conserved domains in the human proteome resulting in higher efficiency of detecting their origins. From these analyses the nature of protein evolution and trends in domain evolution can be observed in the context of the entire human proteome data. The method adopted here also helps delineate the degree of divergence of functional families occurred during the course of evolution. CONCLUSION: This approach to trace the evolutionary origin of functional domains in the human proteome facilitates better understanding of their functional versatility as well as provides insights into the functionality of hypothetical proteins present in the human proteome. This work elucidates the origin of functional and conserved domains in human proteins, their distribution along the Homo sapiens lineage, occurrence frequency of different domain combinations and proteome-wide patterns of their distribution, providing insights into the evolutionary solution to the increased complexity of the human proteome.

Animals↗

PubMed1996

Particulate versus integrated evolution of the upper body in late pleistocene humans: a test of two models.

Evolutionary biologists are largely polarized in their approaches to integrating microevolutionary and macroevolutionary processes. Neo-Darwinians typically seek to identify population-level selective and genetic processes that culminate in macroevolutionary events. Epigeneticists and structuralists, on the other hand, emphasize developmental constraints on the action of natural selection, and highlight the role of epigenetic shifts in producing evolutionary change in morphology. Accordingly, the ways in which these paradigms view and address morphological contrasts between classes of related organisms differ. These paradigms, although seldomly explicitly stated, emerge in paleoanthropology as well. Considerations of postcranial morphological contrasts between archaic and modern humans typically fall into one of two broad interpretive models. The first derives from the neo-Darwinian perspective and holds that evolution in the postcranial skeleton was largely mosaic (operating in a particulate manner), and that temporal change in specific traits informs us about behavioral shifts or genetic evolution affecting isolated anatomical regions (i.e., adaptive behavioral inferences can be made from comparative studies of individual trait complexes). The alternative model follows from the epigeneticist paradigm and sees change in specific postcranial traits as correlated responses to change in overall body form (involving shifts in regulation of skeletal growth, or selective and developmental responses to broad adaptive shifts). By this view, integration of functional systems both constrains and directs evolution of various traits, and morphological contrasts inform us about overall change in body form related to change in such things as overall growth patterns, climatic adaptation, and technological dependency. These models were tested by confirmatory factor analysis using measures of upper body form and upper limb morphological traits in Eurasian Neandertal and early modern fossils and recent human samples. Results indicate (1) a model of morphological integration fits the data better than a model of no integration, but (2) this integration accounts for less than half of the variance in upper limb traits, suggesting a high degree of tolerance for particulate evolution in the context of an integrated upper body plan. Significant relationships were detected between joint shapes and body size, between humeral shaft shape and body size and chest shape, and between measures of biomechanical efficiency and robusticity. The observed morphological differences between late archaic and early modern humans reflect particulate evolution in the context of constraints imposed by genetic and morphological integration. While particulate approaches to interpreting the fossil record appear to be justified, attention must also be paid to delineating the nature and extent of morphological integration and its role in both constraining and producing observed patterns of variation between groups. Confirmatory factor analysis provides a means of examining trait covariance matrices, and serves as a useful method of identifying patterns of integration in morphology.

Biological Evolution↗

PubMed1997

Comparative primate energetics and hominid evolution.

There is currently great interest in developing ecological models for investigating human evolution. Yet little attention has been given to energetics, one of the cornerstones of modern ecosystem ecology. This paper examines the ecological correlates of variation in metabolic requirements among extant primate species, and uses this information to draw inferences about the changes in energy demands over the course of human evolution. Data on body size, resting metabolism, and activity budgets for selected anthropoid species and human hunter-gatherers are used to estimate total energy expenditure (TEE). Analyses indicate that relative energy expenditure levels and day ranges are positively correlated with diet quality; that is, more active species tend to consume more energy-rich diets. Human foragers fall at the positive extremes for modern primates in having high expenditure levels, large ranges, and very high quality diets. During hominid evolution, it appears that TEE increased substantially with the emergence of Homo erectus. This increase is partly attributable to larger body size as well as likely increases in day range and activity level. Assuming similar activity budgets for all early hominid species, estimated TEE for H. erectus is 40-45% greater than for the australopithecines. If, however, it is assumed that the evolution of early Homo was also associated with a shift to a more "human-like" foraging strategy, estimated expenditure levels for H. erectus are 80-85% greater than in the australopithecines. Changing patterns of resource distribution associated with the expansion of African savannas between 2.5 and 1.5 mya may been the impetus for a shift in foraging behavior among early members of the genus Homo. Such ecological changes likely would have made animal foods a more attractive resource. Moreover, greater use of animal foods and the resulting higher quality diet would have been important for supporting the larger day ranges and greater energy requirements that appear to have been associated with the evolution of a human-like hunting and gathering strategy.

Animals↗