Stephen E. Jones

Projects: "Problems of Evolution" (Outline): 8. Cell & Molecular (3)

[Home] [Site map] [Updates] [Projects] [Contents; 1. Introduction; 2. Philosophy (1), (2), (3), (4) & (5); 3. Religion (1) & (2); 4. History (1), (2) & (3); 5. Science; 6. Environment (1), (2) & (3); 7. Origin of life (1), (2) & (3); 8. Cell & Molecular (1) & (2); 9. Mechanisms (1), (2) & (3); 10. Fossil Record; 11. `Fact' of Evolution; 12. Plants; 13. Animals; 14. Man (1) & (2); 15. Social; 16. Conclusion; Notes; Bibliography A-C, D-F, G-I, J-M, N-S, T-Z]

"PROBLEMS OF EVOLUTION": 8. CELL & MOLECULAR
1.	Cell
2.	Molecular
3.	Problem of sex
4.	Eukaryotes
	1.	Endosymbiosis

"PROBLEMS OF EVOLUTION": 8. CELL & MOLECULAR (3)
3.	Problem of sex
Evolution has no adequate explanation for the origin and prevalence of sexual reproduction, e.g "The origin of 
the sexual process remains one of the most difficult problems in biology. (Maynard Smith, 1986, p.35); "What is 
the good of sex? ... is an extremely difficult question for the evolutionist to answer" (Dawkins, 1989, p.43); "the 
evolution of sex ... that problem of problems" (Dawkins, 1991); "Sex is the queen of problems in evolutionary 
biology" (Bell, 1982, p.19; Ridley, 1993, pp.26-27); "One problem is the existence of sex... there is no 
convincing Darwinian history for the emergence of sexual reproduction" (Kitcher, 1982, p.54).

It cannot be claimed that unlike asexual reproduction, sexual reproduction allows variation, because rotifers 
are asexual but have different species, a situation that Maynard Smith called "an evolutionary scandal" 
(Perlman, 2004a).

By "sex" is not meant the mere exchanging of genetic information as prokarytotes (single-cell bacteria) do, but 
rather "sex in eukaryotes" with its "regular succession of meiosis and syngamy" in "the alternation of haploid and 
diploid phases in the life cycle" (Maynard Smith & Szathmary, 1995, p.149). This eukaryote "reproductive model 
[is] quite different from the model mostly adopted by single-celled organisms" and is in fact "exquisitely 
complex," which "is already an immense climb down from what is usually claimed for the theory. ...its `obvious' 
status." (Hoyle, 1987, p.10).

What is meant by "sex" in this context of "the problem of sex," is the "mixing of genetic material from two 
individuals" by "genetic recombination" (ReMine, 1993, p.196). But it is even more than that; sex is a "mixing 
of" half the "genetic material from" each of "two individuals" by meiosis, crossover and genetic 
recombination. "This is called the cost of meiosis": "an asexual parent sends all its genes to each 
progeny" but in "sexual reproduction only half a parent's genes are sent to each of its progeny", so in "the 
Darwinian struggle to pass on more of one's genes to future generations, asexuality is twice as efficient as 
sexuality" (ReMine, 1993, p.197). The evolutionary literature therefore "focuses on the 50% figure as the major 
cause for concern. ... Why is sex so extremely prevalent? Why is it here at all?" (ReMine, 1993, p.197). "This 
question has caused some embarrassment to evolutionary biologists in the past. Although determined to fit 
everything into a selective framework and see shifting gene frequencies as the basis of all evolutionary events, 
they were unable to come up with any satisfactory explanation of the phenomenon that is at once extremely 
widespread and also appears to suffer from a selective disadvantage of quite enormous (50 per cent) proportions." 
(Dawkins, 1986a, p.135). "Despite some ingenious suggestions by orthodox Darwinians there is no convincing 
Darwinian history for the emergence of sexual reproduction.' (Kitcher, 1982, p.54). The "prevalence of sexual 
reproduction in higher plants and animals is inconsistent with current evolutionary theory. ... there is a kind of 
crisis at hand in evolutionary biology" (Williams, 1975, p.v); "The origin of the sexual process remains one of the 
most difficult problems in biology" (Maynard Smith, 1986, p.35); "sex is considered to be one of biology's great 
enigmas" (Bellig & Stevens, 1988, p.ix); "the selective pressures responsible for the origin and maintenance of 
sex is a `big' (maybe the `biggest') unsolved problem in evolutionary biology...there is no consensus about where 
its solution lies... no clear solution emerges" (Michod & Levin, 1988, p.vii); "The mystery about sexual 
reproduction is ... that there is a ... cost of halving the chromosome number and not being able to double the 
number of gametes ... what possible advantage there could be to sexual reproduction that makes up for this cost 
and accounts for its persistence." (Dawkins, 1986a, p.135).

It cannot be claimed that sex is necessary for reproduction because not only single-celled organisms, which 
comprise the vast majority of living things, as well as many plants and animals, reproduce asexually: "Sex is not 
even necessary for continued reproduction. Many single-celled organisms, and some animals and plants, 
reproduce indefinitely without sex. The production of eggs that develop without fertilization is called 
parthenogenesis, or virgin birth. Many insect species consist only of parthenogenetically reproducing females. 
Among reptiles, there are parthenogenetic species consisting entirely of females producing daughters genetically 
identical to themselves. .... Parthenogenesis is even commoner in plants .... Thus, whatever may be the 
explanation of sex, it cannot be said that without it continued reproduction is impossible." (Maynard Smith & 
Szathmary, 1999, p.79); "Our problem is to explain why sex arose, and why it is today so widespread. If it is not 
necessary, why do it?" (Maynard Smit. & Szathmary, 1999, p.80).

"Miracles aside, the Virgin Birth raises another issue dear to the hearts of scientists: why did sexual 
procreation evolve at all? Our most primitive ancestors emerged some 3,850 million years ago, but sex itself 
began only about 1,000 million years ago. Before then, all creatures presumably existed as clones. In his 
book The Evolution of Sex, John Maynard Smith of Sussex University maintains that there is a gap in our 
basic understanding of why sex evolved. `I have been wondering about this for fifty years but I don't claim 
to have solved the problem,' he told me. `The problem has been that, in the short run, abandoning sex would 
be an enormous advantage, at least for females.' Calculation illuminates the joys of reproducing without sex: 
sexually reproducing females on average produce one female offspring, while asexually reproducing ones, 
who rely on virgin births, will produce two. Thus, among a colony of asexually and sexually reproducing 
individuals, the former would quickly dominate. So why is it that females go through all the fuss and bother 
of finding a mate and then dilute their genes with those of a male in any resulting offspring?" (Highfield R., 
"Can Reindeer Fly?: The Science of Christmas," [1998], Weidenfeld & Nicolson: London, 2001, pp.34-35) 

There is a cost of sex, both in its origin and in its maintenance: "The problem is made harder by what has been 
called the 'twofold cost of sex' ... there is a twofold advantage associated with parthenogenesis, or, equivalently, a 
twofold cost of sex." (Maynard Smith & Szathmary, 1999, p.80). "Because the first sexual eukaryotes were 
certainly isogamous, it follows that the twofold cost is a problem only if we are concerned to explain the 
maintenance of sex in later, anisogamous organisms, but not when discussing the origin of sex. All the same, 
there must be some costs associated with sex, even in isogamous organisms. Apart from the necessity of a gamete 
finding a partner with which to fuse, growth and reproduction are interrupted by the complex process of meiosis 
whereby gametes with half the number of chromosomes are produced. To ensure the proper distribution of 
chromosomes, the production of gametes is a complicated process, as anyone familiar with the accounts of 
meiosis in biology textbooks will be aware. Because of these complications, and the obvious disadvantages 
associated with them, it is not surprising that the origin and maintenance of sex continue to be a matter of 
controversy among biologists." (Maynard Smith & Szathmary, 1999, pp.80-81)

Explanations that sex arose for the long-term benefits it conferred are illegitimate in evolution, since evolution is 
a "blind, unconscious, automatic process" that "has no purpose in mind. ...does not plan for the future. ...has no 
vision, no foresight, no sight at all" (Dawkins, 1986, p.5): "Early explanations, that it was 'good for the species' to 
have the variation that is engendered by the mixing and shuffling of sex, had largely to be discarded. It was an 
attractive idea to think that sexual reproduction might result in variation staying in populations so that if the 
environment suddenly changed, the population could 'cope' and have at least some of its members surviving, 
which a uniform asexual population might fail to do. But by the end of the 1960s, the weakness of such 
arguments was generally realized. .... Populations do not harbour deleterious traits against the possibility of future 
benefit. We cannot expect a trait, to use Sydney Brenner's immortal words, to evolve in the Cambrian 'because it 
might come in handy in the Cretaceous'" (Dawkins, 1986a, p.135); Genetic recombination ... enormously expands 
the possibilities of evolutional change ... But this is a long-term, prospective advantage, not an immediate one. 
Natural selection lacks foresight. A trait will not be selected merely because it will have, at some time in the 
future, beneficial effects. It is only present benefits that count." (Maynard Smith, 1986, pp.35-36).

"THE BRILLIANT theoretical physicist Richard Feynman is rumoured to have said, `If you think you 
understand quantum theory, you don't understand quantum theory.' I am tempted by an evolutionist's 
equivalent: `If you think you understand sex, you don't understand sex: The three modern Darwinians from 
whom I believe we have the most to learn - John Maynard Smith, W D. Hamilton and George C. Williams - all 
devoted substantial parts of their long careers to wrestling with sex. Williams began his 1975 book Sex and 
Evolution with a challenge to himself: `This book is written from a conviction that the prevalence of sexual 
reproduction in higher plants and animals is inconsistent with current evolutionary theory ... there is a kind 
of crisis at hand in evolutionary biology ..:' [Williams G.C., "Sex and Evolution," Princeton University Press: 
Princeton, 1975, p.v] Maynard Smith and Hamilton said similar things. It is to resolve this crisis that all three 
Darwinian heroes, along with others of the rising generation, laboured. I shall not attempt an account of 
their efforts, and certainly I have no rival solution to offer myself." (Dawkins R., "The Ancestor's Tale: A 
Pilgrimage to the Dawn of Evolution," Houghton Mifflin Co: Boston MA, 2004, p.424)
The favourite explanation of evolutionists for the origin and prevalence of sex, is the "Red Queen" hypothesis, that 
sex arose as an "arms race" against parasites (Ridley, 1993, pp.61-63). However, that has now been shown to be 
inadequate to "account for the ubiquity of sex" (Otto & Nuismer, 2004; Kettlewell, 2004). 

"A team of British scientists has shown just what is so good about sex, at least in yeast. Yeast comprises 
tiny organisms that reproduce both ways, sexually and asexually. From evolution's standpoint, sexual 
reproduction seems to have many disadvantages over the asexual variety. It wastes time and energy, it 
mixes up perfectly good genes, and females, who do nearly all of the reproduction work, get to pass on only 
half their genetic material. ... Matthew Goddard and a team .... made two different versions of otherwise 
identical yeast, one that could reproduce both ways and one that could only reproduce asexually. The team 
found that under normal conditions, both sorts of yeast fared just as well. But under extreme conditions, the 
sexy yeast did better. "Our results indicate that sexual reproduction can provide a selective advantage 
during adaptation to new environments, and these data are consistent with Weismann's ideas," they wrote in 
the journal Nature. ... ("Sex helps yeast adapt to new situations," ABC, March 31, 
2005)
The "problem of sex" is not that in some (not all - see below) circumstances sexual reproduction can be an 
advantage over asexual reproduction, but how a `blind watchmaker' process `seeking' only its immediate avoidance of 
disadvantage, ever discovered the long-term advantage of sexual reproduction, given its enormous 
immediate costs.

"Geckos that forego sex and instead clone themselves are able to run farther and faster than relatives that 
reproduce the more conventional way. "This is extraordinary," said Kellar Autumn .... "The traditional 
theory is that when a species gives up sex and reproduces through cloning, the offspring will have reduced 
performance." Parthenogenetic animals, which create exact copies of themselves, are all females: mothers 
cloning daughters. Autumn and colleagues studied the parthogenetic Bynoe's gecko from Australia. ... The 
researchers used a state-of-the-art lizard treadmill to test the gecko's speed, body temperature, and calorie 
burning, and compared them to other lizards. The Bynoe's geckos turned out to be much better athletes than 
their sexually reproductive relatives, outperforming them by 50 percent on the treadmill. This was a 
surprise, since a similar study of lizards from the deserts of the United States had shown the opposite trend. 
One of Autumn's coauthors, Michael Kearney, said that some parthogenetic species, like the Bynoe's 
gecko, evolved when two species crossed, or hybridized. Kearney compared these ultra-fit geckos to the 
"super tough" mule, which is a cross between a horse and a donkey. "If there was an Olympic team of 
Bynoe's geckos, there wouldn't be a single male on it," Autumn said. "They are the ‘Xena: Warrior 
Princess' of the lizard world." The findings are in the May/June issue of the journal Physiological and 
Biochemical Zoology. ..." (Schirber M., "Super Geckos Excel without Sex," Livescience, 7 June 
2005)[top]
 
3.	Eukaryotes
	1.	Endosymbiosis
"But Lynn Margulis took the idea further, proposing that at least two other features of the eukaryotic cell 
had been acquired by endosymbiotic means. One was the flagellum, the whip-like structure which propels 
some eukaryotic cells. (Structurally, it is different from and more complex than the cilia of simple cells.) 
Noting that the Protist Myxotricha is propelled by spirochaetes attached to its surface, she proposed that 
flagella are incorporated spirochaetes. Finally in 1970 she completed the picture by suggesting that the 
centriole- the device which separates the chromosomes at cell division - was also of endosymbiotic origin. 
The eukaryotic cell, it seems, is an ogre who has enslaved no fewer than four other organisms to work for it. 
Of course, this daring hypothesis leaves us with numerous problems. How, for instance, did the cell manage 
before it acquired mitochondria? Why is some of the old circular DNA left over in the cytoplasm? Do the 
plastids of plants and the mitochondria of animals have a common origin? And so on. However, we need 
not pursue these technical points. All we need do is register the fact that Darwinian theory scarcely explains 
such an astonishing development. To be sure, to postulate endosymbiosis is not an explanation; it is simply 
a description. It offers no explanation of how meiosis appeared. It does not account for the appearance of 
novel structures such as the nucleolus, the Golgi apparatus, or the microtubules which distinguish the 
eukaryotic cell. Above all, it does not explain how DNA came to be organised into chromosomes and 
enveloped in a nuclear membrane. In short, far too many things seem to have been happening at once for 
chance to be an adequate explanation, and we are left with an enigma." (Taylor G.R., "The Great Evolution 
Mystery," [1983], Abacus: London, 1984, reprint, pp.212-213) [top]