Brain size at birth throughout human evolution: a new method for estimating neonatal brain size in hominins

An increase in brain size is a hallmark of human evolution. Questions regarding the evolution of brain development and obstetric constraints in the human lineage can be addressed with accurate estimates of the size of the brain at birth in hominins. Previous estimates of brain size at birth in fossil hominins have been calculated from regressions of neonatal body or brain mass to adult body mass, but this approach is problematic for two reasons: modern humans are outliers for these regressions, and hominin adult body masses are difficult to estimate. To accurately estimate the brain size at birth in extinct human ancestors, an equation is needed for which modern humans fit the anthropoid regression and one in which the hominin variable entered into the regression equation has limited error. Using phylogenetically sensitive statistics, a resampling approach, and brain-mass data from the literature and from National Primate Research Centers on 362 neonates and 2802 adults from eight different anthropoid species, we found that the size of the adult brain can strongly predict the size of the neonatal brain (r² = 0.97). This regression predicts human brain size, indicating that humans have precisely the brain size expected as an adult given the size of the brain at birth. We estimated the size of the neonatal brain in fossil hominins from a reduced major axis regression equation using published cranial capacities of 89 adult fossil crania. We suggest that australopiths gave birth to infants with cranial capacities that were on average 180 cc (95% CI: 158–205 cc), slightly larger than the average neonatal brain size of chimpanzees. Neonatal brain size increased in early Homo to 225 cc (95% CI: 198–257 cc) and in Homo erectus to approximately 270 cc (95% CI: 237–310 cc). These results have implications for interpreting the evolution of the birth process and brain development in all hominins from the australopiths and early Homo, through H. erectus, to Homo sapiens.     

Relationships between tree size, crown shape, gender segregation and sex allocation in Pinus halepensis, a Mediterranean pine tree

Background and Aims

Sex allocation has been studied mainly in small herbaceous plants but much less in monoecious wind-pollinated trees. The aim of this study was to explore changes in gender segregation and sex allocation by Pinus halepensis, a Mediterranean lowland pine tree, within tree crowns and between trees differing in their size or crown shape.

Methods

The production of new male and female cones and sex allocation of biomass, nitrogen and phosphorus were studied. The relationship between branch location, its reproductive status and proxies of branch vigour was also studied.

Key Results

Small trees produced only female cones, but, as trees grew, they produced both male and female cones. Female cones were produced mainly in the upper part of the crown, and male cones in its middle and lower parts. Lateral branch density was correlated with the number of male but not female cones; lateral branches were more dense in large than in small trees and even denser in hemispherical trees. Apical branches grew faster, were thicker and their phosphorus concentration was higher than in lateral shoots. Nitrogen concentration was higher in cone-bearing apical branches than in apical vegetative branches and in lateral branches with or without cones. Allocation to male relative to female function increased with tree size as predicted by sex allocation theory.

Conclusions

The adaptive values of sex allocation and gender segregation patterns in P. halepensis, in relation to its unique life history, are demonstrated and discussed. Small trees produce only female cones that have a higher probability of being pollinated than the probability of male cones pollinating; the female-first strategy enhances population spread. Hemispherical old trees are loaded with serotinous cones that supply enough seeds for post-fire germination; thus, allocation to males is more beneficial than to females.     

Polar electrophoresis: shape of two-dimensional maps is as important as size

The performance of two-dimensional electrophoresis in conventional gels in Cartesian coordinates (2-DE) vs. polar coordinates (2-PE) is here evaluated. Although 2-DE is performed in much longer Immobiline gels in the first dimension (17 cm) vs. barely 7-cm in 2-PE, an equivalent resolving power is found. Moreover, due to the possibility of running up to seven Immobiline strips in the radial gel format, the reproducibility of spot position is seen to be higher, this resulting in a 20% higher matching efficiency. As an extra bonus, strings of "isobaric" spots (i.e. polypeptides of identical mass with different pI values) are more resolved in the radial gel format, especially in the 10 to 30 kDa region, where the gel area fans out leaving extra space for spot resolution. In conclusion, this novel gel format in the second dimension of 2D gels is seen as an important improvement of this technique, still one of the most popular in proteome analysis.     

Laurina mutation affected Coffea arabica tree size and shape mainly through internode dwarfism

The two varieties—Bourbon (B) and its natural mutant Bourbon pointu (BP)—of Arabica coffee (Coffea arabica L.) differ by an epigenetic, monolocus, and recessive laurina mutation that results in pleiotropic effects, such as tree dwarfism and tree-shape modification. The objective of the study was to search for the origin of the differences in size and shape of the tree both at the macroscopic (length and number of internodes, branching angle) and at the microscopic levels (size and number of cells within the internode pith). At the macroscopic level, the laurina mutation acted only by decreasing the internode size. Neither the angle of branching nor the number of internodes was influenced by the mutation. At the microscopic level, the mutation lowered mainly the number of cells present along the longitudinal axis of the internode, and, at a lesser extent, the cell height. Especially, the internode size decreasing explained both the tree dwarfism and the tree-shape modification. In fact, the laurina mutation strengthened the dwarfism of plagiotropic internodes when compared to that of the orthotropic ones, and such an impact was mainly due to a strong cell number decrease. To summarize, two major pleiotropic effects of the laurina mutation can be explained only by a modification of the trade-off between meresis and auxesis during the internode growth. This opens new perspectives for the characterization of the other effects at the hormonal level, and then, for the identification of the gene at the molecular level.     

Differences in shape and size of skull and mandible in Talpa species (Mammalia: Eulipotyphla) from Turkey

We analysed with landmark-based images morphological differences between four species of Talpa which resemble each other morphologically and are all highly adapted to underground life. Subtle shape differences of the skull and mandibular bones were found between all species. However, there is also broad overlap between all species. Talpa caucasica had the largest skull and mandibles, and Talpa levantis the smallest.     

LAMINA: a tool for rapid quantification of leaf size and shape parameters

Background  

An increased understanding of leaf area development is important in a number of fields: in food and non-food crops, for example short rotation forestry as a biofuels feedstock, leaf area is intricately linked to biomass productivity; in paleontology leaf shape characteristics are used to reconstruct paleoclimate history. Such fields require measurement of large collections of leaves, with resulting conclusions being highly influenced by the accuracy of the phenotypic measurement process.     

Brain size,head size and behaviour of a passerine bird

A recent increase in comparative studies of the ecological and evolutionary consequences of brain size in birds and primates in particular have suggested that cognitive abilities constitute a central link. Surprisingly, there are hardly any intraspecific studies investigating how individuals differing in brain size behave, how such individuals are distributed and how brain size is related to life history and fitness components. Brain mass of the barn swallow Hirundo rustica was strongly predicted by external head volume, explaining 99.5% of the variance, allowing for repeatable estimates of head volume as a reflection of brain size. Repeatability of head volume within and between years was high, suggesting that measurement errors were small. In a 2 years study of 501 individual adult barn swallows, I showed that head volume differed between sexes and age classes, with yearlings having smaller and more variable heads than older individuals, and females having smaller and more variable heads than males. Large head volume was not a consequence of large body size, which was a poor predictor of head volume. Birds with large heads arrived early from spring migration, independent of sex and age, indicating that migratory performance may have an important cognitive component. Head volume significantly predicted capture date and recapture probability, suggesting that head volume is related to learning ability, although morphological traits such as wing length, aspect ratio and wing area were unimportant predictors. Intensity of defence of offspring increased with head volume in females, but not in males. Barn swallows with large heads aggregated in large colonies, suggesting that individuals with large heads were more common in socially complex environments. These results suggest that brain size is currently under natural and sexual selection, and that micro‐evolutionary processes affecting brain size can be studied under field conditions.     

Sex of children and family size: a decision model

Parents often manifest the desire to have children of both sexes, and this wish sometimes influences their actual reproductive behavior. If sibship size were selectively limited once the above objective was achieved, would the sex sequences of completed families still present a random character? In order to answer that question, a decision model reproducing the enlargement strategy of families relative to sex criteria was created. By simulation, it was shown that family limitation based on sex composition entails a positive association between sexes of consecutive children in fictitious families. Such a property has indeed been detected in some samples of real families, thus supporting the present model. However, it may also be attributed to biological factors.     

Organ shape and size: a lesson from studies of leaf morphogenesis

Control of the shape and size of indeterminate organs, such as roots and stems, is directly related to the control of the shape and size of the cells in these organs, as predicted by orthodox cell theory. For example, the polarity-dependent growth of leaf cells directly affects the polar expansion of leaves. Thus, the control of leaf shape is related to the control of the shape of cells within the leaf, as suggested by cell theory. By contrast, in determinate organs, such as leaves, the number of cells does not necessarily reflect organ shape or size. Genetic evidence shows that a compensatory system(s) is involved in leaf morphogenesis, and that an increase in cell volume can be triggered by a decrease in cell number and vice versa. Studies of chimeric leaves also suggest interaction between leaf cells that coordinates the behaviour of these cells at the organ level. Moreover, leaf size also appears to be coordinated at the whole-plant level. The recently hypothesised neo cell theory describes how leaf shape- and size-control mechanisms control leaf shape at the organ-level via cell-cell interaction.     

Anthraquinone derivatives as a new family of protein photocleavers

Certain anthraquinones, which are present in many biologically important natural products, effectively and randomly cleaved proteins (BSA or Lyso) during photoirradiation using a long wavelength UV light without any further additives. It was also found that this ability could be improved by the attachment of a suitable substituent into the anthraquinone core skeleton.     

U-box proteins as a new family of ubiquitin ligases

Ubiquitin-protein ligases (E3s) determine the substrate specificity of ubiquitylation and, until recently, had been classified into two families, the HECT and RING-finger families. The U-box is a domain of approximately 70 amino acids that is present in proteins from yeast to humans. The prototype U-box protein, yeast Ufd2, was identified as a ubiquitin chain assembly factor (E4) that cooperates with a ubiquitin-activating enzyme (E1), a ubiquitin-conjugating enzyme (E2), and an E3 to catalyze the formation of a ubiquitin chain on artificial substrates. We recently showed that mammalian U-box proteins, in conjunction with an E1 and an E2, mediate polyubiquitylation in the absence of a HECT type or RING-finger type E3. U-box proteins have thus been defined as a third family of E3s. We here review recent progress in the characterization of U-box proteins and of their role in the quality control system that underlies the cellular stress response to the intracellular accumulation of abnormal proteins.     

The pregnancy-specific glycoprotein family of the immunoglobulin superfamily: Identification of new members and estimation of family size

The members of the carcinoembryonic antigen (CEA)/pregnancy-specific glycoprotein (PSG) gene family have a characteristic N-terminal domain that is homologous to the immunoglobulin variable region. We have estimated the size of the PSG subfamily by identification of N-domain exons from isolated genomic clones and from total genomic DNA through PCR amplification and DNA sequence determination. The PSG subfamily contains at least 11 different genes. For 7 of these, two DNA sequences differing from each other in 1 to 4 nucleotides were detected. Most likely, they represent different alleles. They are PSG1, PSG2, PSG3, PSG4, PSG5, PSG6, PSG7, PSG8, PSG11, PSG12, and PSG13. Six of the N-domain sequences described here are new. All of the PSGs except PSG1, PSG4, and PSG8 contained the arginine-glycine-aspartic acid sequence at position 93-95 corresponding to the complementarity determining region 3 of immunoglobulin. Parsimony analysis of 24 CEA and PSG sequences using 12 members of the immunoglobulin gene superfamily as outgroups to root the family tree shows that the N-domain of the CEA group genes evolved in one major branch and the PSG group genes in the other.     

Mammalian body size changes and Plio-Pleistocene environmental shifts: implications for understanding hominin evolution in eastern and southern Africa

This study examines geographic and temporal variation in three mammalian taxa co-occurring in eastern and southern Africa. The selected taxa-the spotted hyena (Crocuta crocuta), the plains zebra (Equus burchellii), and the impala (Aepyceros melampus)--are geographically widespread in modern times and are abundant in eastern and southern African Plio-Pleistocene fossil sites. Craniodental measurements of modern conspecifics from known geographic locations are compared using multivariate statistical methods to discern patterns of modern geographic variation within taxa. Modern and fossil samples are statistically compared to assess the nature and extent of inferred shifts in body size, both between modern samples and through time in each region. These results indicate that modern spotted hyenas and plains zebras exhibit mainly size variation between regions, with southern African samples possessing statistically larger craniodental metrics than eastern African samples. Comparison of fossil and modern samples reveals that the fossil assemblages do not show the same pattern of geographic variation. Significant temporal changes are more numerous between fossil and modern eastern African samples, and these changes are not mirrored by similar changes in the southern African samples. The changes experienced by taxa in eastern Africa appear to have been more extreme and wide-ranging than those in southern Africa, a presumed refugium. This result accords well with genetic studies of several large mammal species and paleoenvironmental studies suggesting that eastern African localized environments were more affected by tectonism and volcanism than were those in southern Africa. This study suggests that different evolutionary scenarios may have existed within Africa during the Plio-Pleistocene, but that both regions played unique and complementary roles in the evolution of African hominins and the broader faunal community.     

Classification in LCA: Building of a coherent family of criteria

There is a very close analogy between Life Cycle Assessment (LCA) and decision making tools such as the multicritcria approach. LCA is a particular model of a multicriteria decision making tool which is applied to environmental data. The similarities between LCA and multicriteria decision making tools are highlighted. The strict precision of multicriteria decision making tools is used to improve classification. For this, six dimensions (or axes of significance) of environmental impacts can be distinguished. The aim is to build a coherent family of environmental data from these considerations. Rules for the building of this family are proposed.     

Group size versus territory size in group-living badgers: a large-sample field test of the Resource Dispersion Hypothesis

Badgers ( Meles meles ) have been the focus for the development of a pervasive model of social grouping behaviour, relevant to a number of carnivore species and other taxonomic groups – the Resource Dispersion Hypothesis (RDH). The RDH hypothesises that the dispersion and richness of resources in the environment provide a passive mechanism for the formation of groups, even without any direct benefits of group living. However, few studies have tested the RDH in the field. The principal prediction is that, as opposed to enlargement of territory sizes to accommodate more members, territory size (TS) is independent of group size (GS). Instead, TS is determined by the spatial dispersion of resources, while GS is independently determined by the richness of those resources. However, these predictions provide only weak correlative tests, especially in non-experimental field studies. The first predicts an absence of correlation and is therefore prone to Type II error, especially given the small sample sizes and errors in estimating TS and GS of mammals in the field. We tested for independence of territory size and group size in all years with available data since the beginning of the long-term badger study in Wytham Woods in 1974. We used two methods of TS estimation, a sequential Bonferroni technique to adjust for multiple inference tests, a combined analysis and an analysis with pooled data. This prediction of the RDH could not be rejected on the basis of any of these analyses. Given this evidence that other processes are independently determining group size and territory size, further predictions of the RDH will be worth investigating in considerable detail.