M G BellNovember 23, 2013
Research at UCLA on the coloration and complexity of primate faces (monkeys and apes) has shown that there is a correlation between those attributes and the size of social groups, although the effect was less marked among apes as opposed to monkeys, which is thought to be because apes have a more highly developed set of facial expressions which they can use to aid recognition. Past a certain point, muscular expressivity might be a more flexible way of demonstrating individuality than coloration and physiognomical variation.
"Humans are crazy for Facebook, but our research suggests that primates have been relying on the face to tell friends from competitors for the last 50 million years and that social pressures have guided the evolution of the enormous diversity of faces we see across the group today," said Michael Alfaro, an associate professor of ecology and evolutionary biology in the UCLA College of Letters and Science and senior author of the study.
"Faces are really important to how monkeys and apes can tell one another apart," he said. "We think the color patterns have to do both with the importance of telling individuals of your own species apart from closely related species and for social communication among members of the same species."
"Our research suggests increasing group size puts more pressure on the evolution of coloration across different sub-regions of the face," Michael Alfaro said.
Other variables affected coloration such as distance from the equator and the degree of forest cover (true also of humans), but the degree of facial complexity was linked only to group size.
"We found that for African primates, faces tend to be light or dark depending on how open or closed the habitat is and on how much light the habitat receives," Alfaro said. "We also found that no matter where you live, if your species has a large social group, then your face tends to be more complex. It will tend to be darker and more complex if you're in a closed habitat in a large social group, and it will tend to be lighter and more complex if you're in an open habitat with a large social group. Darkness or lightness is explained by geography and habitat type. Facial complexity is better explained by the size of your social group."
Evidently, one must distinguish between group behaviour linked to mutual protection (such as among shoals of fish or herds of bison) and intra-group 'social' behaviour in which characteristics are attributed to individuals, requiring a mechanism to distinguish one individual from another. But it would be unjustified to make a hard and fast distinction between such types of groups. No doubt there is a continuum of intermediate situations between, at the most basic, a group whose members are simply recognizable as conspecifics because of their size, shape, color, or smell, and a complex social group in which individuals' behaviour towards each other depends on memory of previous interactions with a particular individual, emotional drives and external situations (to pick just a few out of many factors determining inter-personal behaviour).
It is an interesting question, as to how far back up the evolutionary tree animals first became able to distinguish indivuals from conspecifics in general. Do dogs recognize each other? – obviously yes; do lizards recognize each other? – hmmm; do sharks recognize each other? There is a lot we don't know! Dmitri Dergun29th April 2013
Research led by the University of Colorado Boulder seems to show that there are mechanisms in corn reproduction that favour seeds with homogeneous parentage: each seed consists originally of two components, an embryonic corn plant and an endosperm which contains nutrients used in the growth of the embryonic plant. It is possible for these two components to have genetically different 'parents', and the research found that plants whose two components had identical parents grew better than plants where the parentage was different.
CU-Boulder Professor Pamela Diggle says:
"It is fairly clear from previous research that plants can preferentially withhold nutrients from inferior offspring when resources are limited. Our study is the first to specifically test the idea of cooperation among siblings in plants."
"The results indicated embryos with the same mother and father as the endosperm in their seed weighed significantly more than embryos with the same mother but a different father. We found that endosperm that does not share the same father as the embryo does not hand over as much food -- it appears to be acting less cooperatively."
William "Ned" Friedman, a professor at Harvard University who helped conduct research on the project while a faculty member at CU-Boulder, said:
"One of the most fundamental laws of nature is that if you are going to be an altruist, give it up to your closest relatives. Altruism only evolves if the benefactor is a close relative of the beneficiary. When the endosperm gives all of its food to the embryo and then dies, it doesn't get more altruistic than that."
These reports of the results use words like 'mother', 'father', 'cooperation', and 'altruism', which seems anthropomorphic, or whatever the equivalent word would be for the attribution of animal characteristics to vegetables. (Think screaming cabbages!) So let's be clear: this is a chemical mechanism which gives nutritional preference to more closely related organisms. It's a stretch to call it altruism or cooperation; but it does show that evolution favours kinship.
Altruism is most often thought of as a 'groupish' characteristic, ie it evolves to favour cooperation between members of a group, along with empathy and other characteristics of advanced forms of animal species, and it is characterized as a cognitive process.
A zoological definition goes: 'instinctive behavior that is detrimental to the individual but favors the survival or spread of that individual's genes, as by benefiting its relatives'.
No-one is going to credit ears of corn with cognitive abilities, and even the word 'instinct' seems inappropriate; yet it seems that we may need to broaden our understanding of altruism if it can be delivered chemically. On the other hand, everyone is happy to accept the idea that evolution can function as well for corn as for sentient creatures. Perhaps then the reality is that groupishness, or altruism or cooperation or what you will, is something that emerges among all life forms and has bio-chemical underpinnings.By Dmitri Dergun01/11/2010
New research suggests a linkage between live birth and the development of group-related behaviours in a species. Alison Davies, a researcher at the University of California, Santa Cruz, writing in the Proceedings of the Royal Society B: Biological Sciences, describes a species of desert night lizard in the Mojave Desert which lives in family groups and shows patterns of social behavior more commonly associated with mammals and birds.
Davis says that while about 20 lizard species are thought to form family groups, only two of those lay eggs. "Viviparity provides the opportunity for prolonged interaction between the mother and offspring, which predisposes the animal to form a family group," she writes. "The importance of parent-offspring interaction fits with what is currently understood about evolution of family groups and cooperative behaviors in birds and mammals."
The researchers found that the lizards huddle together in kin-related groups. "This is remarkable, given the fact that in most species of lizards, individuals actively avoid each other," Davis said. The groups remain together for years after young lizards are born, and in some cases are multi-generational.
In 1995, Stephen Emlen, the Jacob Gould Schurman Professor of Behavioral Ecology in the Department of Neurobiology and Behavior at Cornell University, published An Evolutionary Theory of the Family (PNAS), in which he described the evolution of family groups in birds and mammals, drawing out similarities across different groups of species. But he did not extend his study to lizards. David says that her results show their groups to have similar characteristics. "Biologically, lizards are very different from both mammals and birds, yet a few species of lizards have evolved a social system around nuclear family members that is nearly identical to what we see in ground squirrels, primates, and woodpeckers," she says.
Davis's co-author Barry Sinervo, Professor of Ecology and Evolutionary Biology at UCSC, says: "Establishing a common pattern for how kin-based groups and cooperative behaviors evolve across different taxa gives us an invaluable tool. It helps us to predict where similar group behaviors may be found in other species," he said.
In the current study, the researchers did not attempt to identify or measure the survival advantages of the lizards' groupish behaviour, but they plan to do so in future. "Determining the fitness consequences of kin-based social groups in this species will be an important next step," Sinervo says.
It's not perhaps very surprising that there are general rules that would apply to cross-species groupish behaviour. Apart from obvious advantages such as preserving warmth, the proximity of conspecifics would seem likely to encourage cooperation and communication. These things are much easier to study in larger animals, evidently. How do you set about identifying cooperation or communication among small bugs that live inside dead logs, for instance? So the fact that groupish behaviour has mostly been described among 'advanced' animals such as mammals and birds doesn't argue for its absence among lower forms of life. And the link with viviparity may be a red herring; obviously there is a causative factor at work in the case of the lizards, but one should not conclude that viviparity is a necessary pre-condition for groupish or kin-related behaviours. Ants and bees disprove that immediately.By Michael Bell19/06/2010
Research recently published in the journal Behavioural Ecology and Sociobiology shows that cockroaches make collective foraging decisions, and that this group behaviour is the more pronounced, the more cockroaches are involved.
Researchers Mathieu Lihoreau (Research Centre for Psychology, School of Biological and Chemical Sciences, Queen Mary University of London), Jean-Louis Deneubourg (Centre National de la Recherche Scientifique, Université de Rennes) and Colette Rivault (Service d’Ecologie Sociale, Université Libre de Bruxelles) gave hungry cockroaches (Blattella germanica) a choice between two identical food sources, and found that the animals chose whichever food source had already attracted the most other cockroaches; the effect became more marked in proportion to the number of cockroaches who had already made the more popular choice.
The researchers say that the selection of food sources 'relies uniquely on a retention effect of feeding individuals on newcomers without comparison between available opportunities', and that the behaviour 'shows similarities with the foraging dynamics of eusocial species, thus stressing the generic dimension of collective decision-making mechanisms based on social amplification rules despite fundamental differences in recruitment processes'.
Although the organization of the cockroach groups is simpler than that of eusocial animals, the researchers hypothesise that such parsimony could apply to a wide range of species.
'Eusocial' is the term used to describe species such as ants and bees in which groups are all related to one another; in the case of the cockroaches kin relationships are not a factor (something that is also true of human groups once they had evolved past the kin-group stage).
The researchers point out that the observed behaviour of B. germanica involves short-range communication between the individual cockroaches, rather than the use of pheronomes or other long-range attractants, although they do not speculate on what type of communication this might be.
The importance of collective behaviour in such life forms as cockroaches comes as something of a surprise to scientists: "What we are realising is that 50% to 60% of insects live in groups and we don't know what is happening in these groups," says Lihoreau.
Perhaps the truth of the matter will turn out to be that group behaviour emerged very early in evolution as an aid to fitness, and that thereafter solitary behaviour was the exception rather than the norm, requiring suppression of the inherent 'groupishness' of precursor species. But we don't know, because researchers haven't been looking for group behaviour in primitive life forms; perhaps now they will begin to! By Michael Bell22/11/2009
Researchers at Yerkes National Primate Research Center (Atlanta, Georgia) have shown that in a population of 70 chimpanzees, a substantial majority of the animals showed a significant bias towards right-handed gestures when communicating.
As is well known, linguistic functions in humans are controlled by the left cerebral hemisphere, and for a long time it has seemed possible that there is some connection between this fact and the predominance of right handedness in humans (resulting equally from left-hemisphere dominance). Anatomical differences at the cellular level between left and right hemispheres have been demonstrated. Many researchers also believe that spoken language had its origins in gestural communication, so that evidence of right-handedness in pre-linguistic communication by chimpanzees is significant.
As reported in the January 2010 issue of Elsevier's Cortex, a team of researchers, supervised by Prof. William D. Hopkins of Agnes Scott College (Decatur, Georgia), studied hand-use in 70 captive chimpanzees over a period of 10 months, recording a variety of communicative gestures specific to chimpanzees. These included 'arm threat', 'extend arm' or 'hand-slap' gestures produced in different social contexts, such as attention-getting interactions, shared excitation, threat, aggression, greeting, reconciliation or invitations for grooming or for play. The gestures were directed at the human observers, as well as toward other chimpanzees.
"The degree of predominance of the right hand for gestures is one of the most pronounced we have ever found in chimpanzees in comparison to other non-communicative manual actions. We already found such manual biases in this species for pointing gestures exclusively directed to humans. These additional data clearly showed that right-handedness for gestures is not specifically associated to interactions with humans, but generalizes to intraspecific communication", notes Prof. Hopkins.
The French members of the team, Dr. Adrien Meguerditchian and Prof. Jacques Vauclair, from the Aix-Marseille University, say: "This finding provides additional support to the idea that speech evolved initially from a gestural communicative system in our ancestors. Moreover, gestural communication in apes shares some key features with human language, such as intentionality, referential properties and flexibility of learning and use".
Hemispheric lateralization of linguistic, and presumably pre-linguistic skills is a fact, but there is no satisfactory answer to the question of why it should have evolved. It doesn't seem likely that it was to solve a capacity problem, although that remains a possible explanation. More convincing is the idea that there is an advantage to handedness. William H. Calvin, in The Throwing Madonna: Essays on the Brain, speculated that one-handed throwing could have been the crucial advance that gave early humans their survival advantage as against other apes, and that the requirement for intricate sequencing of motor actions was best fulfilled in one hemisphere and was then taken advantage of by language when it came along. But really this is just an elaboration of the capacity argument, and more convincing (but only just) is the idea that in gestural communication there is a group advantage if everyone gestures with the same hand, to avoid the need to apply a mirror transformation to the gestures you see when they are made by a left handed person, with some possible dangers of misinterpretation.
Whatever the original reasons for handedness, meaning left-brain dominance in certain functions, the fact that humans are mostly right-handed is of course just a random result. Evolution had to pick either left or right, and metaphorically it spun a coin, which happened to land right side up.
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