Cooperative feeding and breeding, and the evolution of executive control

Dubreuil (Biol Phil 25:53–73, 2010b, this journal) argues that modern-like cognitive abilities for inhibitory control and goal maintenance most likely evolved in Homo heidelbergensis, much before the evolution of oft-cited modern traits, such as symbolism and art. Dubreuil’s argument proceeds in two steps. First, he identifies two behavioral traits that are supposed to be indicative of the presence of a capacity for inhibition and goal maintenance: cooperative feeding and cooperative breeding. Next, he tries to show that these behavioral traits most likely emerged in Homo heidelbergensis. In this paper, I show that neither of these steps are warranted in light of current scientific evidence, and thus, that the evolutionary background of human executive functions, such as inhibition and goal maintenance, remains obscure. Nonetheless, I suggest that cooperative breeding might mark a crucial step in the evolution of our species: its early emergence in Homo erectus might have favored a social intelligence that was required to get modernity really off the ground in Homo sapiens.     

Middle pleistocene humans from africa

Patterns of human evolution in the Middle Pleistocene remain poorly understood. There is general consensus that by the onset of this time period, populations ofHomo erectus were dispersed from Africa into Eurasia, including the Far East. In the western part of this range (perhaps in Africa),Homo erectus then produced a daughter lineage exhibiting more advanced characters of the face, braincase and cranial base. How this new species should be defined is currently debated. In my view, fossils from sites such as Bodo and Broken Hill in Africa may be lumped with material from earlier Middle Pleistocene localities in Europe. Such a taxon is appropriately namedHomo heidelbergensis. Whether the hypodigm should be extended to include fossils from China is another question. In any case, this group of hominids is plausibly ancestral to both the specialized Neanderthals of Europe and more modern humans of the later Middle Pleistocene.     

Homo erectus: Ancestor or evolutionary side branch?

Controversies in paleoanthropology wax and wane, but substantial interest is currently focused on Homo erectus. This species has traditionally been regarded as a member in good standing of the human family, where it is placed as an evolutionary intermediate between earlier Homo habilis and later Homo sapiens. Recently, however, some workers have questioned whether the species exists at all. If its populations have been transformed slowly toward the modern condition, and if continuity with living people can be demonstrated in many geographic regions, then any separation of Homo erectus from Homo sapiens must be largely arbitrary. In that case, only one species should be recognized and this slowly changing lineage would have to be called Homo sapiens. Other paleontologists adopt a different view, arguing that Homo erectus is not only anatomically distinctive but also restricted in its geographic distribution. They claim that the fossils from Java and China are so specialized in appearance that they cannot lie in the mainstream of human evolution. Homo erectus, strictly defined as limited to the Far East, probably went extinct without issue. If so, more modern populations must have evolved from another source, perhaps one outside of Asia altogether.     

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.     

Antiquity and Social Functions of Multilevel Social Organization Among Human Hunter-Gatherers

Three levels of social organization are recognized among human hunter-gatherers: the community, the domestic unit, and the band. We describe the key features of these three levels and show how they are intimately connected. We hypothesize that, in the course of human social evolution, bands emerged as a level of social organization within existing communities. As predators, hunter-gatherers live at lower population densities than chimpanzees (Pan troglodytes), even where the two species are sympatric. We propose that band formation evolved in humans from the more transient fissioning behavior seen within chimpanzee communities as a solution to the conflicting pressures of sustaining higher levels of cooperation required in hunting and the division of labor in a more dispersed community. If disputes break out, or if resources in the band territory are temporarily depleted, the existence of a wider community continues to be adaptive. To reconstruct the evolution of band society, we draw upon four lines of evidence: group (or network) size predicted from neocortex ratios, the distance materials were moved from their source during various periods in hominin evolution, ethnographic data on hunter-gatherer daily foraging ranges and population densities collated by the authors, and fossil hominin morphology. From these data, we conclude that key features of modern human hunter-gatherer social organization probably appear in the course of the evolution of Homo heidelbergensis.     

Out of Africa and back again

If the genusHomo did indeed originate in Africa, then it must have spread by about 2 m.y. ago into Asia where it is represented at 1.8 m.y. ago byHomo erectus fossils. This latter species in turn eventually spread back into Africa, as indicated by the 1.4 m.y. old OH 9 calvaria from Olduvai, and into Europe, as indicated by the 800,000 year old Ceprano calvaria from Italy. These hominids are associated only with Oldowan style artefacts of cores, choppers and flakes and were apparently not conversant with Acheulean handaxe technology. It seems that they most probably evolved viaHomo heidelbergensis into the Neanderthals. Meanwhile, a completely separate development originating withHomo ergaster of about 1.7 m.y. ago in Africa and possessing Acheulean handaxe technology evolved via such forms as Ndutu and Steinheim intoHomo sapiens.     

Who Killed the Neanderthals?

Homo neanderthalensis, evolved from the European populations of H. heidelbergensis, and shows some special morphological traits, probably due to an adaptation to particular climatic conditions. It also appears that H. neanderthals had a specialized diet which was mostly carnivorous. Anatomically modern humans of the European Upper Palaeolithic seem to differ from the alimentary behaviour that characterized the Neanderthals; their diet was more varied, with a greater contribution from freshwater alimentary resources (molluscs and fishes). Comparison between the various strategies of subsistence adopted by the two species allows us to propose a hypothesis about the extinction of H. neanderthalensis.     

LB1’s virtual endocast, microcephaly, and hominin brain evolution

Earlier observations of the virtual endocast of LB1, the type specimen for Homo floresiensis, are reviewed, extended, and interpreted. Seven derived features of LB1's cerebral cortex are detailed: a caudally-positioned occipital lobe, lack of a rostrally-located lunate sulcus, a caudally-expanded temporal lobe, advanced morphology of the lateral prefrontal cortex, shape of the rostral prefrontal cortex, enlarged gyri in the frontopolar region, and an expanded orbitofrontal cortex. These features indicate that LB1's brain was globally reorganized despite its ape-sized cranial capacity (417 cm³). Neurological reorganization may thus form the basis for the cognitive abilities attributed to H. floresiensis. Because of its tiny cranial capacity, some workers think that LB1 represents a Homo sapiens individual that was afflicted with microcephaly, or some other pathology, rather than a new species of hominin. We respond to concerns about our earlier study of microcephalics compared with normal individuals, and reaffirm that LB1 did not suffer from this pathology. The intense controversy about LB1 reflects an older continuing dispute about the relative evolutionary importance of brain size versus neurological reorganization. LB1 may help resolve this debate and illuminate constraints that governed hominin brain evolution.     

Reconstitution 3D par Computerized-tomography (CT) et endocrâne virtuel du crâne 5 du site de la Sima de Los Huesos (Atapuerca)

The 3d Ct reconstruction and virtual brain endocast of Cranium 5 from the site of “La Sima de los Huesos” (Atapuerca), allows us to get new information to increase the study and knowledge of Homo heidelbergensis population, and to compare this specimen with others in the fossil record, in order to understand the evolutionary process of the brain, focusing on the middle Pleistocene period. Furthermore, we can observe the changes this species (Homo heidelbergensis) has undergone, at least in Sima de los Huesos population making comparative studies with African and Asian middle Pleistocene specimens. We have used the new data to compare European Homo heidelbergensis represented by SH5 with Kabwe, a controversial specimen considered by some authors like the African Homo heidelbergensis representative, in order to establish the similarities and differences between both specimens.     

NOVEL COOPERATION EXPERIMENTALLY EVOLVED BETWEEN SPECIES

Cooperation violates the view of “nature red in tooth and claw” that prevails in our understanding of evolution, yet examples of cooperation abound. Most work has focused on maintenance of cooperation within a single species through mechanisms such as kin selection. The factors necessary for the evolutionary origin of aiding unrelated individuals such as members of another species have not been experimentally tested. Here, I demonstrate that cooperation between species can be evolved in the laboratory if (1) there is preexisting reciprocation or feedback for cooperation, and (2) reciprocation is preferentially received by cooperative genotypes. I used a two species system involving Salmonella enterica ser. Typhimurium and an Escherichia coli mutant unable to synthesize an essential amino acid. In lactose media Salmonella consumes metabolic waste from E. coli, thus creating a mechanism of reciprocation for cooperation. Growth in a spatially structured environment assured that the benefits of cooperation were preferentially received by cooperative genotypes. Salmonella evolved to aid E. coli by excreting a costly amino acid, however this novel cooperation disappeared if the waste consumption or spatial structure were removed. This study builds on previous work to demonstrate an experimental origin of interspecific cooperation, and to test the factors necessary for such interactions to arise.     

Fission-fusion and the evolution of hominin social systems

The course of hominin evolution has involved successive migrations towards higher absolute latitudes over the past three million years. Poorer habitat quality further from the equator has led to the necessity for groups occupying higher latitudes to live at lower population densities. Coupled with a trend towards increasing group size over this time period, this tendency towards expansion has led to exponential increases in the area requirements of hominin groups, and a concomitant need to adjust foraging patterns. The current analyses suggest that the development of increasingly complex, multi-level fission-fusion social systems could have freed hominins of the foraging constraints imposed by large group sizes and low population densities. Analyses of the fossil record suggest latitudinally-driven differences in area requirements of the australopithecines from East and South Africa, and African and Asian Homo erectus. In contrast, chronologically-driven differences appear between H. erectus as a whole and Homo heidelbergensis, and between H. heidelbergensis and the Neanderthals. These results are discussed in relation to studies of the foraging patterns of primates and hunter-gatherers.     

Loss of air sacs improved hominin speech abilities

In this paper, the acoustic-perceptual effects of air sacs are investigated. Using an adaptive hearing experiment, it is shown that air sacs reduce the perceptual effect of vowel-like articulations. Air sacs are a feature of the vocal tract of all great apes, except humans. Because the presence or absence of air sacs is correlated with the anatomy of the hyoid bone, a probable minimum and maximum date of the loss of air sacs can be estimated from fossil hyoid bones. Australopithecus afarensis still had air sacs about 3.3 Ma, while Homo heidelbergensis, some 600 000 years ago and Homo neandethalensis some 60 000 years ago, did no longer. The reduced distinctiveness of articulations produced with an air sac is in line with the hypothesis that air sacs were selected against because of the evolution of complex vocal communication. This relation between complex vocal communication and fossil evidence may help to get a firmer estimate of when speech first evolved.     

Genome digging: insight into the mitochondrial genome of Homo

Background

A fraction of the Neanderthal mitochondrial genome sequence has a similarity with a 5,839-bp nuclear DNA sequence of mitochondrial origin (numt) on the human chromosome 1. This fact has never been interpreted. Although this phenomenon may be attributed to contamination and mosaic assembly of Neanderthal mtDNA from short sequencing reads, we explain the mysterious similarity by integration of this numt (mtAncestor-1) into the nuclear genome of the common ancestor of Neanderthals and modern humans not long before their reproductive split.

Principal Findings

Exploiting bioinformatics, we uncovered an additional numt (mtAncestor-2) with a high similarity to the Neanderthal mtDNA and indicated that both numts represent almost identical replicas of the mtDNA sequences ancestral to the mitochondrial genomes of Neanderthals and modern humans. In the proteins, encoded by mtDNA, the majority of amino acids distinguishing chimpanzees from humans and Neanderthals were acquired by the ancestral hominins. The overall rate of nonsynonymous evolution in Neanderthal mitochondrial protein-coding genes is not higher than in other lineages. The model incorporating the ancestral hominin mtDNA sequences estimates the average divergence age of the mtDNAs of Neanderthals and modern humans to be 450,000–485,000 years. The mtAncestor-1 and mtAncestor-2 sequences were incorporated into the nuclear genome approximately 620,000 years and 2,885,000 years ago, respectively.

Conclusions

This study provides the first insight into the evolution of the mitochondrial DNA in hominins ancestral to Neanderthals and humans. We hypothesize that mtAncestor-1 and mtAncestor-2 are likely to be molecular fossils of the mtDNAs of Homo heidelbergensis and a stem Homo lineage. The d_N/d_S dynamics suggests that the effective population size of extinct hominins was low. However, the hominin lineage ancestral to humans, Neanderthals and H. heidelbergensis, had a larger effective population size and possessed genetic diversity comparable with those of chimpanzee and gorilla.     

Origin of the Genus <Emphasis Type="Italic">Homo</Emphasis>

The origin of the genus Homo in Africa signals the beginning of the shift from increasingly bipedal apes to primitive, large-brained, stone tool-making, meat-eaters that traveled far and wide. This early part of the human genus is represented by three species: Homo habilis, Homo rudolfensis, and Homo erectus. H. habilis is known for retaining primitive features that link it to australopiths and for being the first stone tool makers. Little is known about H. rudolfensis except that it had a relatively large brain and large teeth compared to H. habilis and that it overlapped in time and space with other early Homo. Our understanding of the paleobiology and evolution of the larger-brained H. erectus is enhanced due to its rich fossil record. H. erectus was the first obligate, fully committed biped, and with a body adapted for modern striding locomotion, it was also the first in the human lineage to disperse outside of Africa. The early members of the genus Homo are the first to tip the scale from the more apish side of our evolutionary history toward the more human one.     

Resource abundance and the critical transition to cooperation

Cooperation is abundant in nature, occurring at all levels of biological complexity. Yet cooperation is continually threatened by subversion from noncooperating cheaters. Previous studies have shown that cooperation can nevertheless be maintained when the benefits that cooperation provides to relatives outweigh the associated costs. These fitness costs and benefits are not fixed properties, but can be affected by the environment in which populations reside. Here, we describe how one environmental factor, resource abundance, decisively affects the evolution of cooperative public goods production in two independent evolving systems. In the Avida digital evolution platform, populations evolved in environments with different levels of a required resource, whereas populations of Vibrio cholerae evolved in the presence of different nutrient concentrations. In both systems, cooperators and cheaters co‐existed stably in resource‐rich environments, whereas cheaters dominated in resource‐poor environments. These two outcomes were separated by a sharp transition that occurred at a critical level of resource. These results offer new insights into how the environment affects the evolution of cooperation and highlight the challenges that populations of cooperators face when they experience environmental change.     

Why are some numerical concepts more successful than others? An evolutionary perspective on the history of number concepts

From the history of mathematics, it is clear that some numerical concepts are far more pervasive than others. In a densely multimodular mind, evolved cognitive abilities lie at the basis of human culture and cognition. One possible way to explain the differential spread and survival of cultural concepts based on this assumption is the epidemiology of culture. This approach explains the relative success of cultural concepts as a function of their fit with intuitions provided by conceptual modules. A wealth of recent evidence from animal, infant, and neuroimaging studies suggests that human numerical competence is rooted in an evolved number module. In this study, I adopted an epidemiological perspective to examine the cultural transmission of numerical concepts in the history of mathematics. Drawing on historical and anthropological data on number concepts, I will demonstrate that positive integers, zero, and negative numbers have divergent cultural evolutionary histories owing to a distinct relationship with the number module. These case studies provide evidence for the claim that science can be explained in terms of evolved cognitive abilities that are universal in Homo sapiens.     

The evolution of altruistic social preferences in human groups

In this paper, we consider three hypotheses to account for the evolution of the extraordinary capacity for large-scale cooperation and altruistic social preferences within human societies. One hypothesis is that human cooperation is built on the same evolutionary foundations as cooperation in other animal societies, and that fundamental elements of the social preferences that shape our species'' cooperative behaviour are also shared with other closely related primates. Another hypothesis is that selective pressures favouring cooperative breeding have shaped the capacity for cooperation and the development of social preferences, and produced a common set of behavioural dispositions and social preferences in cooperatively breeding primates and humans. The third hypothesis is that humans have evolved derived capacities for collaboration, group-level cooperation and altruistic social preferences that are linked to our capacity for culture. We draw on naturalistic data to assess differences in the form, scope and scale of cooperation between humans and other primates, experimental data to evaluate the nature of social preferences across primate species, and comparative analyses to evaluate the evolutionary origins of cooperative breeding and related forms of behaviour.     

Fossil Humankind and Other Anthropoid Primates of China

More than 70 sites have yielded human fossils in China. They are attributed to Homo sapiens erectus and Homo sapiens sapiens. The earliest one is possibly about 1.7 Ma. A series of common morphological features, including shovel-shaped incisors and flatness of the face, characterize them. There is a morphological mosaic between H. s. erectus and H. s. sapiens in China. The existence of common features and the morphological mosaic suggest continuity of human evolution in China. That there are a few features which are more commonly seen in the Neanderthal lineage, occurring in a few Chinese fossil skulls, probably suggests gene flow between China and the West. Based on them, in 1998 I proposed an hypothesis—continuity with hybridization—for human evolution in China. The hypothesis is supported by paleolithic archeology, and it supports the multiregional evolution hypothesis of modern human origins. The anatomically modern humans of East Asia originated most probably in China. Although some nonhuman anthropoid primates of China—Gigantopithecus, Sivapithecus, Ramapithecus and Lufengpithecus—have been suggested as the direct ancestors of human beings, the discovery of more specimens and further studies do not support these suggestions. Therefore, it is most probable that the transition between apes and humans did not occur in China.