Why sex exists?
Sex is ubiquitous among living organisms, but the rise of sexual reproduction is a polemic subject in evolutionary biology and no broad consensus has emerged yet. Diverse concepts have been used to explain the ubiquity of sex and its success in biological evolution, but none passed the experimental tests of computer simulations of evolution demonstrating that sexual reproduction is superior to asexual reproduction. Asexual reproduction is simple, fast and convenient when mutations produce the needed variance. Popular propositions that suggest that sex accelerates evolution to maintain sexual species one step ahead of asexually reproducing parasites, the so-called Red Queen hypothesis, or that sex uncouples beneficial from deleterious mutations, allowing selection to proceed more effectively compared to organisms without sex, do not explain the emergence of sex in computer simulations.
An alternative view states that sex allows for cooperation between different partners, each specialised in a specific strategy to harvest nature. Computer simulations show that this cooperation allows partners to achieve synergies that make them hugely successful, shifting the odds of evolutionary adaptation to favour the selection of sexual organisms. The computer experiments demonstrate that this explanation of the evolution of sex is robust. The existence of sex and its emergence through natural selection during biological evolution can be easily explained by assuming the existence of synergy between the sexes, as evolution will favour the division of reproductive labour between them.
The production of synergy in the interaction between sexes is widespread. Examples can be found starting with gametes. Female gametes normally optimise resource accumulation to feed the newborns, sacrificing mobility, while male gametes optimise mobility and exploratory behaviour sacrificing resource accumulation. The sexes often complement each other’s gametes, providing an increased resistance to pathogens. Organisms show enormous variations in sex roles among species. Among mammals, the female lactates to produce milk for babies and the male protects both female and baby. A Pandora’s box of role differences among sexes, that allow synergies to crystallise, awaits discovery.
The agent based computer simulations
The simulations uses the program Biodynamica, a robust metaphor for biological evolution. The model creates populations of agents or virtual organisms, each possessing a genome with different genes. Each gene has an allele coding for a specific behaviour or other phenotypic characteristic. For example, one gene codes for the type of sexual strategy the agent will employ so that five different alleles code for either: asexual reproduction by cloning; monosexual reproduction by thelytoky; bisexual reproduction, as among most living organisms, including gametogenesis and mitotic recombination; haplo-diploidy where females were diploid and males haploid as in the Hymenoptera; and “hermaphrodites” practising facultative sex, so that they out-crossed with a male or with another hermaphrodite. Another gene codes for ploidy (number of sets of chromosomes in the genome), with alleles for either haploidy, diploidy or haplo-diploidy. The simulation for sexual diploids reproduction included explicit simulation of gametogenesis, mitosis, meiosis, and crossovers between parents’ gametes during fertilisation and mutations.
A publicly accessible version of Biodynamica allows the interested person to do evolutionary experiments themselves.
Recognising the importance of synergy in the efficient working of social interactions and of society, opens a treasury of examples and diversity of cooperative strategies. Biologists and sociologists have focused more on the conflict between the sexes forgetting the base upon which they work: synergistic cooperation. Synergy and competition drive evolution, but synergy seems to be the prime mover of most of the interesting processes that affect all type of society.
A corollary of this work for social synergy in general, is that societies that aim to equate integration of individuals to a reduction in conflict, might reduce the social synergy that arises from diversity. Striving for equity by equating the value of the different ways of participating in society might favour synergies; but eliminating or diminishing the diversity of roles in society will decrease the efficiency of social cooperation by decreasing the synergies that can be achieved. Not all diversity arises from sexual roles. Sophisticated societies achieve diversity in a variety of other forms in addition to the sexual kind and thus open multiple routes to synergies. This sounds like insights gained by the Scottish economist Adam Smith long ago about the effect of division of labour on the efficiency of the working of markets.
The new insights gained through empirical experimentation and hypothesis testing using computer simulations allows us to bridge the gap between Biology, Sociology, Anthropology, Economics and Physics, creating a novel interdisciplinary space to advance our understanding of our society and that of other living beings. Dr Jaffe has published a book “The Roots of Synergy” which introduces the layman to this fascinating new scientific field, promoted by a small group of scientists from very different fields, that has already produced important novel insights in economic sciences and sociobiology.