The Origin of Sex: Why All is Fair in Love and War

Chris King

Sep 2017 Genotype: 1.0.7 - PDF

http://dhushara.com

 

Contents

 

The Fundamental Question

 

Have you ever seriously asked where did sex actually come from? How come we are all saddled with the mortal condition, where we only transmit half our genes to each member of the next generation we sire, rather than living in parthenogenetic heaven forever? How did things end up this way? And why the endless attraction to the other half of reality, like a moth circling to its doom into the flame of desire? They say all's fair in love and war, as if sexual love is a fundamental conflict of interests, but what does that mean? What kind of fairness are we actually talking about? And how did these delicate terms of engagement originally arise? I'm going to take you on a journey of discovery, but first we need to make a connection to the first life on Earth that became life as we know it, LUCA, the last universal common ancestor.

 

Left: Orion with organic gas clouds and a condensing solar system exploded from the small rectangle in the centre view into the insets.

Right: Murchison meteorite with relative amino acid abundances.

 

The Biogenic Wave-Particle Universe

 

Life isn't an accident of fate, but an interactive cosmic destiny. It's inscribed in the laws of nature and the quantum physics of the chemical elements spawned in the stardust of supernovae and the endlessly complexifying molecules formed by catalytic processes. All phenomena in the universe are governed by a deep complementarity between the continuous and discrete wave and particle aspects of the quantum, which define energy in terms of frequency and invoke an archetype of the symmetry-broken complementarity we find in the ovum and sperm. Molecules obey the laws of quantum physics and their wave orbitals interact in a cascade of cooperative bonding effects, in a form of spatial quantum computation, demonstrated by the complex three dimensional structures of protein and nucleic acid molecules and their fractal interaction to form organelles and tissues.

 

On a galactic footing, if you examine the gas clouds of the great nebulae like Orion, you can literally see solar systems being born and you can also see the signature of huge gas clouds of primordial organic molecules like hydrogen cyanide and formaldehyde that can interact under suitable conditions to form the very organic polymers that make up proteins and the ribonucleic acids (RNAs) forming the information messengers in our cells today.

 

We also know the Earth was bombarded by comets and meteorites from the primal gas cloud forming the solar system and that these also contain precursors of the molecules of life, including amino acids and nucleic acid bases, which rained down on the early Earth in copious quantities. But none of these scenarios show how these precursors wouldn't have been destroyed by radiation, atmospheric, volcanic and other processes without a nurturing stable environment promoting the formation of complex molecules over geological timescales.

 

Lost City vents, pores concentrating organics and olivine sand grains from Hawaii..

 

Lost City Gardens of Eden

 

Enter the real nail unhinging Pandora's box of life - something quite surprising - a chemical Garden of Eden that has been bubbling away on the sea floor since our liquid oceans first condensed. The universe is replete with a ubiquitous green semi-precious mineral called olivine, a form of magnesium iron silicate. It is a predominant mineral in the Earth's crust and is also found on the Moon, on mars, on asteroids and comets and you can even detect it raining down on a star in Orion's belt sufficientlyfor its signature to be seen from Earth's telescopes. The thing about olivine is that it is alkaline and the Early Earth had a high CO2 atmosphere, making the ocean acidic, so that the two together form a fizzy, reactive chemical garden that generates organic molecules and bioenergetic precursors like hydrogen and methane. But the really intriguing thing is that the fizzy columns of these chemical gardens are full of pores that can concentrate organics right up to biological concentrations and they have been doing this throughout Earth's history and are still doing so at the Lost City vents and other sites, so they continue to form a steady reactive energetic interface, which would have been even more prevalent on the early planet.

 

Left: Life in the transition from chemical garden pores to cells.
Right: Rickettsiae and Methanococcoides illustrate bacteria and arachaea.

 

Life Before Cells becomes Two Founding Domains

 

This ties in superbly well with what we can discover from tracing the known life forms back genetically towards their origin. We are all familiar with bacteria because they are the source of many of the world's most devastating diseases, but there is another branch of life called archaea, which until recently were just thought to be an odd extreme group of bacteria. The archaea have geological habitats - ocean hydrothermal vents, geothermal mud pools, extremely salty environments, the bottom of oil wells and in the guts of cows and termites, making the methane that glows in swamps as the 'will of the wisp' and threatens to exacerbate global warming and climate change. But unlike bacteria, none of the archaea are pathogens. Initially they were just thought to be archae-bacteria or ancient bacteria, but we now know they are another life form altogether. For example their enzymes to make DNA are different from those of bacteria, although their genetic codes and respiring electron transport systems are related. Even more significant, the membrane components making up the cell wall of archaea are chemically different and unrelated to those of bacteria. This kind of genetic evidence tells us two things. Firstly that the archaea and bacteria arose as RNA-based life forms before DNA became used as a more stable storage medium for genetic information, unlike RNA which can also act as a catalyst like proteins do. Secondly and even more significantly it tells us that bacteria and archaea diverged before the first cells formed and escaped their nurturing chemical garden pores into the wider world. So replicating life came before cells and began sequestered in these fizzy vents.

 

Left: Two bacteria conjugating via a plasmid-encoded sexual pilus.

Right: Viral bacteriophages injecting their genes via icosahedral syringes.

 

Enclosing Boundaries Make Sexual Transgressors

 

Today we have cells and viruses, but in the beginning we had a mass of interacting RNAs in what is called a progenote - a kind of cooperative genetic soup, in which most of the molecules depended on one another's existence for life to continue. This is reminiscent of the Tantric creation myth of Shakti representing nature and Shiva representing consciousness caught delicto flagrante in deep sexual union, until, as they separated, both consciousness and matter became fragmented into our individual experiences and all the phenomena of the physical world flowed forth. But once you draw a boundary around anything, you divide the totality into included and excluded domains. So the cells became the prokaryotes - bacteria and archaea - and the excluded domain became the viruses.

 

In response, the excluded domain of viruses became parasitic on the cells, trimming down their genomes to just the genes needed for invasion and replication, depending on the cell's metabolic machinery to do everything else in their life cycle. In return viruses and their related transposable genetic elements such as conjugation plasmids became agents of genetic exchange, integrating with and altering cellular genomes in the process, so each became informationally dependent on the other. This arrangement performs a key role of sex, to recombine genomes to create new viable forms and functions, and to exorcise deleterious mutant genes. It has become oddly sexual, with plasmids and viruses playing the role of 'transmitting' element and cells a female role of 'accepting' organism. Some plasmids even form a conjugation tube to spool DNA from one bacterium or archaeum to another, even across species, promoting wholesale genetic exchange. Passage through cells also enables viral genomes to recombine, as we see with influenza outbreaks.

 

Left: Most core protein-forming genes existing today evolved by 3 bya ago, with a wave of subsequent losses in some branches and ongoing gene duplication, once the eukaryotes emerged. The green indicates horizontal transfer by viral type sexuality, which has remained ongoing throughout. Above right: Cellular and stromatolite fossils 3.7-3.5 bya with modern stromatolite above centre. Below: Hypothetical colonial eukaryote fossils 2.1, 1.5, 1.6 bya.

 

Hadean Emergence to Oxygenation Catastrophe

 

The liquid oceans formed about 4.1 billion years ago, and the first fossil evidence of life goes back 3.7 at least to cells and cyanobacterial mats called stromatolites. Between then and 3 billion years ago there was a huge explosion of new genes, resulting in the vast majority of the metabolic and functional genes we find today, indicating that life had diverged radiatively and become a significant player in Earth's dynamics. You can calculate the age of these events with reasonable certainty using cross-species genetic analysis. We might have heard nothing more about this story had not another 'quantum leap' occurred in the emergence of life. The advent of the double photon oxygen-forming  photosynthesis in cyanobacteria resulted in the transformation of the oceans and geological landscape into an oxidised state.  By about 2 billion years ago, oxygen had begun to enter the atmosphere in sufficient quantity to provide a high-energy environment for respiring bacteria - the great oxygenation catastrophe! At the same time, archaeal habitats in the sediments remained highly reducing at the opposite end of the energy landscape. Somewhere between 2.1 billion years ago,  where there is just one enigmatic fossil and 1.6 billion years ago, when we see the first evidence of red algae, an explosive change had happened to the diversity of life on Earth.

 

Left: Mitochondrion in a cell. Right: Kidney cell with nucleus surrounded by dense energetic mitochondria.

 

The Cohabitation Crisis

 

This explosive event was endosymbiosis. The result was the third domain of life, the higher cells, or eukaryotes.  What we now realize occurred was that a high-energy respiring bacterium entered into a symbiotic relationship with an archaeum living inside it to form the mitochondrion. Mitochondria are the energy batteries of oxidation and reduction that are in every cell of our bodies and power our respiration using membrane electrochemistry. It's hard to determine whether this was a parasitic process of invasion of a host, or a case of being consumed alive by an archeal predator, but it was ultimately a mutually beneficial relationship that transformed the energy and information processing capacity of the cell out of sight. The result was that all traces of the founding organisms have since been wiped off the face of the Earth by the new hyper-efficient order of cells with emerging features very similar to our own cells, including the nuclear envelope containing many chromosomes, spindles to draw them apart neatly in pairs, cellular organelles, amoeboid motion and the gobbling actions of phagocytosis.

 

Description: MacintoshHD:Users:chrisking:Desktop:nucleus1.jpg

Left: Before the current arrangement, where the vast majority of eukaryote genes are held in the nucleus, there was a great migration of mitochondrial genes (blue) to the safety of the nucleus. This means the endosymbiont was much more complicated than might appear from the current tiny circular mitochondrial genome (right) and originally contributed most of our metabolic genes.

 

The Great DNA Migration

 

All the indications are that the lion's share of our metabolic genes were once the property of the mitochondrial ancestor and only our informational processing, structural and architectural genes came from the archaeum. But over millions of years, the mitochondrial genes got transferred to the safety of the nucleus, leaving behind only a bare skeleton of essential genes. However, we can still infer which living species are closest to the last eukaryote common ancestor LECA using genetic analysis. We can identify α-proteobacteria as having similarities with mitochondrial derived genes, and an archaeum related to the Lokiarcheota as having genetic relationships with key eukaryote genes involved in processes such as DNA repair, cell architecture and membrane budding. Unfortunately no one has yet seen what Lokiarchaeota looks like, although we do know about other archaeal species, because they are free-living and their genes have been recovered from deep ocean trenches in a shotgun genetic snapshot. The human nuclear genome has 3 billion base pairs coding 19,000-20,000 genes, but the mitochondrion now has only 16,569 bp with 37 key genes. It's original genome would have been between 1 and 4 million bps with around 800-2,500 genes, based on comparable α-proteobacteria. Lokiarchaeota, has 5 million bp coding 5,381 genes.

 

Left: The Hydrogen hypothesis. Right: Archaea congregating with mitochondria inside an algal cell.

 

H is for Hydrogen

 

A key theory - the "hydrogen hypothesis" - explains that the two organisms had neatly compensating means of gaining energy that goes right back to those chemical gardens where life first emerged long before eukaryotes. The mitochondria of some sophisticated alpha-proteobacteria today, such as Rhodobacter, can use both photosynthesis and respiration and also can live in both aerobic and anaerobic conditions. In the anaerobic state, they can support a reaction that produces hydrogen and carbon dioxide. These are precisely the food of life for archaeal methanogens, so the two would form a naturally symbiotic couple. You can still find archaea with bacteria congreting around them in this way, as well as archaea that enter algae and congregate with the mitochondria. On the other side of the evolutionary divide, certain of the anaerobic eukaryotes, like Giardia, that people used to think were ancient founding members because they lacked functioning mitochondria, actually support organelles called mitosomes and hydrogenosomes. Some hydrogenosomes have demonstrable genetic homology with mitochondria, cementing the retrospective side of the hypothesis.

 

Wiping the Slate Clean

 

The end result of this process, as we have noted, is that a new paradigm emerged from the anaerobic sediments, in which the eukaryote cell combined the vastly increased power of the respiring energy metabolism in the high energy environment of the great oxidation catastrophe combined with the information processing power of RNA-enriched nucleic acid processing of the archaeum.  Like the origin of life, we have marginal indication of the precursors or even the immediate progenitors of this event, because the huge evolutionary pressures and the sheer success of the revolution wiped all traces away in the unrivalled dominance of the new advanced cell line.

 

Left: eukaryote cell with internal organelles. Right: Mitosis showing ordered chromosome separation.

Meiosis requires two stages of mitosis and homologous recombination between paternal and maternal genomes.

 

The Arcade of Mysteries

 

This leaves us with several major mysteries. The higher cells, leading to plants, animals and fungi, have multiple chromosomes which they can tease apart using microtubule spindles, forming a perfect, complete new genetic complement gene by gene by mitosis, protected inside the nuclear envelope during the active part of the cell cycle. They have elaborate internal organelles to generate highly reactive enzymes and keep all their reactive molecules from damaging the cell and its DNA. They have a complex architecture of microtubules and muscular actin fibres. They have complex membrane signaling, including receptors used by the neurotransmitters we find in the brain. They can swallow other cells in amoeboid phagocytosis and they have a unique flagellum that has a real whiplash, unlike the simple rotary flagellae of bacteria and archaea. All of these features appear to have emerged very rapidly under the evolutionary pressures of the first flush of eukaryote radiation, so that even the single celled organisms, as close as we can find to the root, have essentially the same apparatus as our own human cells.

 

Naegleria gruberi and some of its functions.

 

Getting Close to the Root

 

If we want to look at a living cell as close as we can find to LECA, the free-living amoebo-flagellate  Naegleria gruberi found in ocean water is a leading candidate. Naegleria shows at or near the root of many evolutionary trees for specific proteins. This organism, closely related to the amoeba that causes encephalitis in hot pools, already contains virtually all the features we find in sophisticated cells like our own, including G-protein coupled signaling receptors, ion channels and active transporters which have now become essential for neurotransmitter function in the human brain. All eukaryotes which were once believed to be simpler archaic forms such as Giarda are now known to be highly evolved specialized cells which have lost their primal versatility. Moreover Naegleria has two modes of existence, one flagellated like the sperm and the other amoeboid and engulfing like the ovum.

 

Left: Principal branches of the eukaryote tree showing prospective root points. Right: Both Giardia and Trypanosomes some of the most elementary eukaryotes,

have evidence of sexual recombination. Upper: Internal recombination between twin nuclei. Lower: Yellow sexual recombinants of green and red strains..

 

Sex From the Word Go!

 

In addition, virtually all eukaryotes, including the Naegleria group are at least intermittently sexual and have the elegant graded gene-matching sexual recombination of meiosis that we see in forming human sperms and eggs today. Over and above the sheer energy of endosymbiosis, it is this which has made multicellular life, intelligent animals and human conscious existence possible. A careful investigation of the full spread of eukaryote organisms shows that those few species that are asexual have originated from sexual founding species. Even lowly Giardia and Trypanosomes show evidence of sexual recombination. The core life cycle of both single-celled and multi-cellular eukaryotes is clonal mitotic division intermittently punctuated by sexual reproduction, often due to genetic, or environmental stresses, which require new vital genetic recombinations. Even the human life cycle consists of a huge number of mitotic divisions during development before we produce sperms and eggs by meiosis and procreate.

 

An Inside Job of Sexual Provocation

 

So the idea is that sex as we know it may have been provoked by the early mitochondrial endosymbiont, partly as a means to avoid becoming trapped in a host that became weak from mutations or was at risk of imminent death, possibly with the help of viruses or plasmids, which are natural agents of recombination, as we have seen with bacteria. Certainly the mechanism of controlled cell death, or apoptosis, in all animals including ourselves, is driven by the mitochondria, so there is irrefutable evidence for a lingering control over our very mortality held by these bacterial fellow travellers. Significantly, some key meiosis genes involved in DNA recombination go back before the eukaryotes to our archaeal ancestors, where they are involved in repairing double-stranded breaks in DNA, supporting an initial role of sex as a means to correct genetic damage which may have been at a premium in the high energy free-radical metabolic environment of the early eukaryote cell. Meiosis may also have arisen from mitosis to compensate for cell fusion in the amoeboid archaeum, as it requires an initial nuclear division to create a tetraploid genome, before recombining and subdividing twice by mitosis, into four haploid gametes.

 

Founding plants animals and fungi as well as single-celled choanozoa and apicomplexa have sexually-polarized oogamy. The mycetozoan slime mold illustrates isogamy.

 

Sperms and Eggs Dominate the Field

 

There are two kinds of fertilisation, isogamy and oogamy. Oogamy is the polarised form of fertilisation we humans have, in which the sperm contributes only the father's DNA and the ovum has both the mothers DNA and a complete cytoplasm with mitochondria and all the other cell's organelles. Oogamy is not just confined to animals, but applies as well to our single celled choanoflagellate ancestors, to algae and green plants all the way from the charophytes founding land plants, through mosses and ferns to ginkos and cycads, with seeds and pollen being an adaption to land dispersion. It applies likewise to the Chytrids the earliest true fungi and many of the single celled amoebo-flagellates. So why is life like this and how did it all come about? This kind of inheritance means the mitochondria and their genes are inherited exclusively down the maternal line, while the nuclear genes come from both parents. This acts to prevent an all out mitochondrial war between the paternal and maternal lines, as we shall see. Subsequently this polarisation of sex into gender, in which one sex bequeaths all the founding cellular matrix except for the father's DNA, the ovum formed an organismic template for cell division and became the foundation of multicellular animal embryogenesis, the basis for the layering of the tissues into ectoderm, mesoderm and endoderm, in an imploding wave of cellular subdivisions of the whole mother cell.

 

Mutually antagonistic co-evolution: (a) Male beetle raping the female by puncturing her abdomen. (b) Duck corkscrew penis opposed by a convoluted vagina indicates adaption to female defences against rape. Sex determination: Human X and Y chromosome. The Y is a remnant originally paired with the X. Only a few genes are  homologs and still participate in recombination. The other Y genes have to survive through maintaining backup copies. (d): Wrasses have sex determination by dominance. The dominant female undergoes a sex change to a male.

 

The Perils of Unisex

 

In isogamy there are two anatomically identical gametes trying to fertilise one another, although they may have genetic protocols which determine the sexual type to avoid inbreeding. For example, in yeast, the a and α types always mate with one another and not with themselves. Two main branches of protists, Rhizaria and Chromalveolate also include isogamous organisms. However, unless an isogamic organism has a specific trick to recombine the mitochondrial genes from the two parents, they will go to war. Such a war saps the resources of the newly-forming embryo. The alga Vulva, or sea lettuce, isogametes enter into a mitochondrial war to the death. In the single-celled alga Chlamydomonas reinhardtii, up to 95% of the mitochondrial DNA is destroyed by the opposing party. Both yeasts and slime molds have a cunning way around this, forcing the mitochondria to recombine. Phaesarium, which has 13 sexes rather than two, uses a viral type plasmid to perform mitochondrial recombination. Fungi have pushed their hyphae around the problem in a different way, by using conjugation tubes for fertilisation, which only let the nucleus through to the accepting strain. They can then have huge numbers of sexes, up to 27,000 in one species of bracket fungus. In animals and all the species using sperm-ovum fertilisation, the paternal mitochondria are exorcised, either their entry to the egg prevented, or they are summarily executed shortly after arrival.  Of course a few do escape, leading to a variety of mitochondrial genetic diseases in humans, who can end up becoming a kind of mitochondrial chimera.

 

The African Eve traced by mitochondrial DNA analysis to a San woman.

Right: The Khoisan tree has branches to two San groups running back to 150,000 yrs ago.

 

Two Parents but Only One Embodied Mother

 

The end result is uni-parental mitochondrial inheritance. Through it, we have become polarized into just two fusion sexes, a transmitting sex and an accepting sex. The accepting sex is the female, who conveys not only her nuclear DNA to her offspring, but all the mitochondria, cell organelles and the whole cytoplasmic bag of tricks that makes the development of the early embryo possible. The transmitting sex becomes the male and transmits only nuclear DNA. Uni-parental inheritance of mitochondria is how we know we came out of Africa and are all descended from the Mitochondrial Eve, a woman around a hundred and fifty thousand years ago who was related to the San Bushmen. Because of mammalian XY sex chromosome inheritance, we can also check the males' Y-chromosome Adam, who lived more recently further to the north in Ethiopia. More recently because men have more variance in their reproductive success than women, all of whom can in principle become pregnant.

 

Collapse in Y-chromosome diversity over 8 world regions caused by dominant males taking

control of a disproportionate number of female reproductive partners resulting in a 1:17 ratio.

 

All's Fair in Love and War

 

From then on, the sex wars continue unabated, because the female always has a vastly greater investment in parenting and its resources and the male a greater investment in sowing wild oats by any manner of means possible. The devastating sexual attacks of male fruit flies to poison and injure the female to reduce sperm competition from other suitors, male beetles who rape the female by penetrating her carapace, or the opposing cork-screw vaginas and penises of ducks and drakes, show that the term mutually antagonistic co-evolution is a strategic understatement. Bearing live young, rather than just eggs is in itself a polarising reason why 97% of mammal species are polygynous and only 3% are socially  monogamous, and we know that, even in socially monogamous species, the females are not reproductively monogamous and seek clandestine outside encounters if they get a chance, to avoid putting their eggs all in one basket.

 

 

Left and centre: Humans are a highly polarized species sexually.

Right: A woman is vulnerable at full term. Childbirth carries a significant risk to survival.

 

Men and Women at a Polarising Extreme

 

In a way, we humans are at an extreme of this polarisation, because the female has to not only face a massive vulnerable pregnancy, but, given our large brains, significant risk to her survival giving birth, breast feeding a helpless infant, and many years of long-term child-rearing. By contrast a man can seek to be a resourceful husband, a potentate holding a harem, or choose to cut and run to sow wild oats elsewhere. But fear of paternity certainty has also become a mortal affliction of the human male, which one can see in all the tortured manifestations of history and religion. In the dire punishments of stoning for adultery, the veiling and sequestering of women and female genital mutilation, these deep fissures and lethal frictions continue to erode the quality of human life. The advent of patriarchal dominance is etched in our genes, causing a collapse of human Y-chromosome diversity, as some men gained huge reproductive advantage over others. The reproductive sex ratio collapsed from a historical level of one reproducing male to two females, accounting for the wider natural variation in male reproductive success, to one man to 17 women under the agricultural overlords. One in 200 men today still possess the Y chromosome of Genghis Khan.

 

Malaria and sickle cell anemia result from a Red Queen race of mutually antagonistic co-evolution between sexually reproducing organisms.

 

The Red Queen on Parasites

 

Throughout sexual evolution, another kind of sex war has continued unabated as well, which explains why a two for one disadvantage in transmitting only half our genes to each offspring may benefit them in even greater measure. Like the conflicts of sexual polarization, co-evolution with our parasites is another mutually antagonistic form of what is called a Red Queen race, as in Lewis Carroll's Alice - running an ongoing evolutionary race while standing still with respect to one's opposite and nemesis. Many of our parasites and diseases are caused by sexual eukaryote protists and others are caused by bacteria and viruses that practice the wholesale sexual recombination we explored earlier in prokaryotes, in turn, making human sexuality obligatory for survival. One reason why sex continues to survive is not just that it avoids ratcheting mutations, or provides new viable individuals, but because any clonal organism is a potential helpless victim of any parasite that adapts to it. So clonal species run a risk of being completely wiped out. The variation provided by a sexually diverse population makes it almost impossible to wipe out a sexual organism and results in an endless Red Queen race of mutual adaption between sexual parasites and their equally sexual hosts. Such an evolutionary race between humans and the plasmodium of malaria has led to the preservation of the allele for haemoglobin gene HgbS, which causes the recessive genetic disease sickle cell anaemia when we have two mutant alleles, but helps resistance to malaria infection in those who carry only one copy.

 

Left: Transposable element evolution in the human genome going back to the mammalian radiation shows the long-term coevolution.

Nearly half our DNA is transposable in origin, compared with around 1% protein coding genes and 8% regulating these.

Top right: HERV-K particles (red) expressed along with OCT4 (cyan) a key embroygenesis stem factor.
Lower right: Syncitin expression in the human placenta (green fluorescence).

 

Viruses in Dark Corners

 

A final theory of the origin of sex takes its inspiration from the viral recombination we have seen occurs in prokaryotes. All multicellular organisms have their DNA flooded with endogenous viruses and transposable elements, which, in humans, occupy far more of the genome than protein coding genes. Several of these are as ancient as multicellular organisms and have a life cycle timed to meiosis. The nuclear genome tries very hard to avoid these transposable free-riders with names like LINE-L1, Alu and HERV, or human endogenous retrovirus, from multiplying during meiosis, so there is another kind of arms race here, which is a continuation of the same viral type sexuality we saw in prokaryotes extended to eukaryotes. But transposable elements are far from junk DNA. Their repeated occurrence and that of their gene inducers make for coordinated changes that enable high level co-regulation of developmental genes, so they have become essential participants. Our immune versatility depends on a recombinase RAG. The RAG proteins were originally derived from a DNA transposon in fish. L1-associated genomic regions are hotspots for somatic variantion in the brain, contributing to somatic mosaicism, which may facilitate neuronal plasticity. HERV-K, the one remaining fully active strain, is expressed in human embryos, from the 8-cell stage to the blastocyst, coinciding with expression of the stem factor OCT4, indicating a key role in normal development. The budding gene of the protein syncitin from the human endogenous retrovirus HERV-M has been incorporated into our life cycle to enable the placenta to form a huge multinuclear membranous partition for nutrients to cross to the fetus without mixing of maternal and fetal blood and these virus particles can visibly break out during embryogenesis. While the fusion involved in fertilisation is vastly older, key genes facilitating fusion sex may also have originally come from, or via, transposable elements. Critically, retroelements such as LINE-1 making DNA from an RNA intermediate are held in check in the germ line by an RNA silencing mechanism which utilizes three proteins including four distinct components, two from a bacterial phage contained in the endosymbiont, and two from the founding archaeon, placing the origin of this whole Red Queen race right back at LECA's emergence.

 

Left: The Wife of Bath. Right: From ovum through zygote to blastula, development occurs by fractal division of the maternal cytoplasm. Once polarised sperm-ovum fertilization arose from mitochondrial competition in single celled eukaryotes, it became the foundation enabling the emergence of multicellular animals, where global morphogenesis is necessary to establish the topology of the embryo.

 

What Women Want

 

So what is the hidden lesson in this story? In Chaucer's Canterbury tale, "The Wyf of Bathe", Queen Guinevere entreaties the anti-hero, who has raped a fair young maiden, to save his life, by answering the question "What do women most desire"? It is recorded that in 1380 associates of Chaucer stood surety for an amount equal to half his yearly salary, for a charge of "de rapto" – the rape, or abduction, of one Cecilia Chaumpaigne, so this story goes right to the heart of the matter. The answer is reproductive sovereignty – a sovereignty that exists from two billion years ago, with the endosymbiosis that made complex life possible and endowed women with the role of carrying the energy bearing mitochondria and maternal ovum, which forms the continuity of cellular life and the matrix for multicellular embryogenesis. This is the holy grail answer to our organismic mortality. We became conscious sentient beings because endosymbiosis resulted in the ovum carrying both enough energy to power complex organisms and the cellular matrix for the organism and because the ensuing sexual recombination enabled us to line up and swap our genes to limit the ravages of mutation and to introduce wholly new combinations of individual. Each of us is thus unique and can live in this extraordinary universe and wonder at our fate, because of the altruistic nature of sex, in transmitting only half our genes, and because of the asymmetrical transaction of oogamy that conveys both the energy that propels us and has made the topological development of the multicelled embryo possible, leading ultimately to brains and conscious existence. This sovereignty has continued to play a key role in the evolutionary paradigm, as we shall see next.

 

San Bushman family. Mutual mate choice in a context where female reproductive choice is allowed to olay its key part.

San cave painting celebrating a girl's rite of menarche Fulton Cave (1000 BC), acknowledging the power of fecundity.

 

Why Female Reproductive Choice Matters

 

There is a very real reason for human societies to accept the natural principle of female sovereignty and allow unconstrained female reproductive choice as a human right. Although some of our genes may be homozygous (the same gene on both chromosomes in a pair), inbreeding saps individual fitness because some genes need to have two different alleles for the organism to survive and flourish and some have a huge variety of key alleles. MHC histocompatibility genes, determining how tissues maintain their integration, come in hundreds of alleles and immune resistance is very much a function of maximal diversity among the immune alleles. The same is likely for genes involved in brain development. Female mice outcross with alien males rather than their home group around half the time and when they do, their offspring have far greater allele diversity and better fitness than when inbred. Human females can detect the allure of alien MHC genes form the smell of underarm sweat and also make intuitive choices to optimize outcrossing unless they are already pregnant, or are on a progesterone pill, when the situation becomes reversed. Social control of female reproductive choice by conservative patriarchal societies and religions not only prevents women finding the fittest and most intelligent resourceful partner they can, but, as well as giving men paternity certainty, is designed to ensure marriages preserve in-group family, clan and tribal allegiances. This leads to a variety of detrimental genetic consequences, from lower fitness and intelligence, to genetic diseases

 

Mutual three-strategy prisoners dilemma matrix for the two sexes showing how patriarchal dominance can divide

the women into faithful wives and scarlet whores, repressing female reproductive choice (Independent women centre).

 

Sex and the Prisoners' Dilemma

 

And what of the enigma of love and the heady uncontrollable infatuation of falling in love? The prisoners' dilemma is a strategic paradox where two accused prisoners are each tempted to betray one another, to avoid a light sentence if they stick to their story, and instead go free, by turning state's evidence, but the temptation causes them both to defect against one another and go down for a severe punishment. Sex is a prisoners' dilemma game in which male and female, despite their manifold differences are utterly dependent on the other for the survival of their genes and the very existence of their living offspring.

 

One of the main driving forces of human mental prowess is Machiavellian intelligence, the endless sturm and drang of confidence building amid subtle deceit and spin, that enables a large number of individuals all to find a niche in a complex society, when compensated for by long-term judgment of good character.

 

The "All's fair" proverb in its earliest form, applied specifically to the use of Machiavellian intelligence in a courtship battle between two suitors for the love of another:

 

Love and warre are all one. .. It is lawfull to use sleights and stratagems to .. attaine the wished end (Don Quixote II Cervantes 1620).

 

But the real antidote to the corruption and betrayal strategic expedience can bring is the undeniable beauty of the mating mind. All of the best qualities, in astute mating choice, artistic adornment, textile design, social prowess and physical beauty among the females, with expert hunting, good husbandry, spellbinding story telling and captivating music, among the males, fulfilling resourceful family life. This way the sexes enter together into the conflagration - the ultimate bonfire of the vanities -  the age old quest to fulfill ourselves in the birth of new life, consecrated by coital union with our sexual complement and strategic nemesis in the opposite sex.

 

This remains our one and only immortal compensation for the mortality of existence and the most altruistic transaction nature has seen fit to contrive, to confound our delusions of eternity that no clonal being can ever accomplish.

 

Comparing sexual evolution with our immediate neighbours. Left: Both chimp and bonobo penises have penis bones and penile spines (one shown inset top left) with a very short copulation time of several seconds. The human penis is manifestly larger and testes smaller than sexually promiscuous chimps. Right: Bonobo female in overt estrus. Bonobs have a large clitoris enabling frequent female-female erotic contact. The human clitoris is smaller but highly sensitive with more nerve endings than the human penis. Chimp society is dominated by the alpha male, but females will clandestinely go 'on safari' with chosen males. The less violent sister species bonobos have strong females and the alpha male tends to be big momma's son. Bonobos use social sex to relieve stress e.g. at the sight of food.

 

The Co-evolution of Love

 

So the human sex the wars haven't been all bad. Human sexual co-evolution over evolutionary time has not been an antagonistic love affair. In fact the mating mind is its highest expression in facilitating constructive resourceful reproductive complementarity - the evolutionary realities underpinning how humanity emerged as a super-intelligent social species. The combined effects of female reproductive choice and mutual mate choice attest to a Red Queen race, in which neither sex had the upper hand, and each has had to run while standing still to seek the acceptance of the other - the idea of strategic sexual paradox.

 

Our physiology and our psyche has evolved to be able to love sexually. Homo sapiens has evolved through mutual mate choice in a social environment where female reproductive choice was able to be exercised.

 

Our 'peacock's tail' is thus our super-intelligence played out between the sexes in mutual mating choice, without patriarchal dominance limiting the ability of females to make astute reproductive choices, thus compromising the evolutionary paradigm. There is an intriguing twist to this. Mammalian XY chromosome inheritance results in pure X males, while females with XX have to collapse one X in their somatic cells such as the brain, becoming a genetic chimera, with only their germ line remaining double X. This means that men have greater variance in intelligence because some significant brain development genes are X-linked and female reproductive choice can weed out the best X linked intelligence genes with their daughters benefitting as well. So women astutely judging men's performance is not just about gender roles, it's a fundamental part of how sexual selection works in mammals.

 

Perennially Enticing Sexuality

 

Human females have become perennially sexually receptive and initiate and accept sexual intercourse outside their fertile period of ovulation. And, rather than declaring their estrus to the males as chimpanzees do, to avoid infanticide, human ovulation has become concealed, giving females more power over reproductive choice. Females have in turn, through male reproductive choice, evolved to be more neotonous, to indicate nubility and for their pendulant breasts to express sensuous fecundity. They are capable of ecstatic orgasmic pleasure and they can innately seek outcrossed exotic males, especially when ovulating. Given adequate freedom of choice they will choose fit, smart, resourceful and considerate mates. Unlike the penises of apes, the human penis has no bone and copulation can occur only through a genuine indication of sexual fitness and passionate attention. It is also larger and more sensual than ape penises. Human love making has become a prolonged transformative sensual encounter. Gatherer-hunter society became a foundation for sexual complementarity, in which women provided 85% of the diet and men proved their sexual worth by eloquent  story telling, strategic resourcefulness and skillful hunting.  Although this highly beneficial mutually paradoxical phase of co-evolution eventually became eclipsed by patriarchal dominance in the agricultural epoch, our emergence as a species attests to the reproductive autonomy of women and to the very quality of the life-fulfilling phenomenon we call love.

 

Lakshmi temple Khajuraho: Spiritual maithuna on the high arcades, but deviant depravity on the lower friezes.

Reproductive sex is the raison d'etre, giving social sexuality its true meaning, without which, social sex becomes mere gratification.

 

Fascination, Transgression and Fulfillment

 

This endowment means we have sex as an endless social fascination and intrigue, amid all the convolutions of fidelity and jealousy, trust and betrayal. But this is a gift that means we have the ability to know one another, deeply, intimately and passionately. Social sexuality and the sexual relationship has developed into the central binding cohesive affirmation that gives society its heart and soul. And social sex rules supreme, numerically. A person may have sex ten thousand times in their adult life and yet may only reproduce two to ten offspring at most. This has given us in the world to develop our diverse erotic personae, innocent, forthright and frankly deviant, because sexual intercourse is a boundary-breaking transgression at its very core.

 

But while consenting adult mutual sexual choice, in a mature civilized culture, including choice of sexual orientation, needs to be respected as a human right, the central unifying purpose of sex - the raison d'etre - remains reproductive sexuality, with all its themes of the Song of Songs unfolding in the fertility of new life. It is this that is the ultimate fulfillment of the union of Shakti and Shiva, in the perpetuity of the generations. and it is in this perpetuity that our immortality as conscious beings, as a people and a species is realised.