Fragment. Warren Fahy
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a sperm cell, but it’s actually a tailed protozoan called Euglena viridis. It is an individual animal, a unique species, a single-celled organism remarkably similar to sperm. The primordial sea had produced the first creatures with the ability to hunt, using thrashing tails to chase down other single-celled organisms and consume them. Sometimes these first predators actually exploited the reproductive systems of their prey to facilitate their own reproduction–and sometimes their prey perpetuated itself by hijacking the genes of its attacker.
‘In either case, the proposition of tonight’s Chat is that these very first hunters and their prey created a new and mutually beneficial relationship that we call sex. When certain cells began to specialize in consuming or penetrating other cells for reproduction, others cells specialized in hosting reproduction itself, thus deflecting death and perpetuating both lines of DNA. Sex is the peace treaty between predator and prey. The offspring of their union not only combined the properties of both but carried forward each original single-celled organism, now modified as sperm and egg. So there you have the kindling for tonight’s Fire-Breathing Chat, ladies and germs. I submit that sex began at the very beginning with single-celled organisms. I propose that the answer to the age-old question, which came first, the chicken or the egg, is the egg…and the sperm.’ Geoffrey stepped aside from the podium and bowed.
Shouts came from the back of the auditorium. Uncomfortable groans rose from the scientists in the front rows, especially from the gray hairs.
Geoffrey clicked to the next slide–a human egg wreathed by wriggling sperm–and he paused to enjoy the slightly nervous titter of recognition that the image always evoked from an audience.
‘Egg and sperm may actually be the living echo of a revolutionary moment that transpired a billion and a half years ago in the ancient seas of Earth. Indeed, I propose that this original love story has repeated itself in an unbroken chain since reproduction began in eukaryotic cells–that is, cells that have membrane-enclosed nuclei inside them. When the first hunter cells grew tails in order to chase down their prey, the hunted cells made peace, if you will, by absorbing the hunter’s DNA and facilitating its reproduction, thus ensuring both cells’ survival and turning a war into a partnership.
‘And since the sharing of genetic material led to a convergent variation in the morphology of their offspring, this innovation accelerated the evolution of superior forms in tandem, continuing to ensure the survival of both kinds of original cell in male and female carriers. And the elaboration of multicellular life issuing from that ever-accelerating partnership would launch both of the original organisms into wildly diverse environments.’
The grumblings grew louder in the audience. Geoffrey raised his voice mildly.
‘I suggest that this proposition is validated each time sperm penetrates an egg and results in an offspring. All complex life may have developed simply to stage this age-old dance of two single-celled species. From octopi to humans to whales to ferns, countless expressions of life on Earth stage this original single-celled rendezvous, just as it occurred in ancient seas, in order to reproduce.’
The audience muttered and shuffled as Geoffrey reached his peroration.
‘So why are such complex animals beneficial for continuing the partnership of sperm and egg? Because, ladies and gentlemen, unlike sperm and egg, animals can exploit an amazing variety of changing conditions and environments through evolution. We sexually reproducing animals are an astonishingly diversified fleet of sperm-and-egg-carriers that bring the ancient seas with us into ever-new environmental frontiers.
‘Of course, such elaborate vehicles were also beneficial to the replication of the original single-celled organisms because they have more fun replicating than single-celled organisms. There’s nothing like improved incentives to increase output. But I think we’ll leave that topic for another chat.’
Geoffrey bowed once again, this time to an enthusiastic ovation, unfazed by the jeers and scowls from the front row.
Now the real fun began. He took the first torpedo from a particularly vexed colleague right in front of him. ‘Yes, Dr Stoever?’
‘Well, I don’t know where to begin, Geoffrey,’ the baldheaded scientist drawled forlornly. ‘Sex began with isogamous gametes: two sex cells of the same size fusing together and joining their DNA, which then divided into more cells with a recombination of the two cells’ genes. It did not begin with ancestors of sperm and egg! I’ve never heard of such a preposterous theory!’
‘That is the general assumption,’ Geoffrey replied cheerfully. ‘But everyone concedes that very little is known about the details. I’m sure you’re aware of Haeckel’s theory, Dr Stoever?’
‘Ontogeny recapitulates phylogeny, of course–everyone is aware of Haeckel’s theory, Geoffrey.’
There was a smattering of laughter at this and Geoffrey raised his hand to the audience. ‘Well, just to remind everyone, for a long time scientists observed that during certain phases of development the human embryo looks remarkably like a tadpole, with a tail and gills, and continues to go through other stages that appear to be entirely different animals. What Haeckel proposed is that embryonic development is actually a recapitulation of an animal’s evolutionary past.’
‘Haeckel’s theory has been discredited,’ yelled one scientist from the back row.
‘It only applies to the development of embryos, anyway,’ protested another. ‘Not to sperm and ova!’
‘Ah.’ Geoffrey nodded. ‘Why not? Think outside the box, Dr Mosashvili. And Haeckel is far from being discredited, Dr Newsom. In fact, this proposition, if it proves correct, might well be his final vindication.’
‘You can’t claim sperm and egg are merely echoes of the first eukaryotic cells,’ shouted another irate scientist.
‘Why not?’ Geoffrey volleyed.
‘Because sperm and egg are unlike any other organism. They carry only half the chromosomes!’
‘Which they combine to produce the next stage of their development,’ Geoffrey returned, ‘which, I propose, may be the carrier stage, if you will–which naturally became more and more specialized to reach new environments. The fact that sperm and egg carry only half the chromosomes of their offspring could be a further effect of specialization to symbiotic reproduction, or it could be proof that sex began with separate organisms that combined and doubled the amount of their chromosomes to make sexually differentiated carriers of each original cell. I submit that Haeckel’s principle is not only right, but may not have been taken far enough.’
‘But originating as a predator/prey relationship…I don’t buy it.’ Dr Stoever was scowling.
‘Look at bees and flowers,’ Geoffrey replied. ‘When insects invaded the land, they devoured plant life. But plants adapted to the invasion. They turned insects into agents of their own reproduction by offering nectar in flowers and seeds in fruit. Examples abound of predator/prey relationships becoming symbiotic relationships, even reproductive relationships. Every one of us is a colony of cooperative organisms, millions of which inhabit our intestinal tract, graze on our epidermises, and devour bacteria scraped by our eyelids off our eyeballs, between the columns of our eyelashes. All of these creatures had to have begun as predators but then adapted in cooperation with our bodies so as not to destroy their own homes, and in fact to help their hosts survive and flourish. Without the vast horde of creatures that inhabit us, we would die. We could not have evolved without them, nor they without us. Instead of a perpetual war, I believe this treaty of cooperation is the true theme of life, the very essence of a viable ecosystem. Instead of the stalemate of a war, which many believe the natural world reflects, perhaps evolution is always working toward stability, peace treaties, the mutual benefit of alliances. And its central building block is the treaty between the first single-celled predator and its prey: sex. That peace treaty had to be struck before the relentless violence of predator and prey inevitably selected both for extinction, which probably happened many times.’
‘The development of sex in eukaryotic cells is still a mystery,’ grunted another grizzled scientist. He shook