shenzhou

There is a response to Roughgarden's article in 'California Wild' that can be found here: http://www.calacademy.org/calwild/2006winter/stories/sex.html Her Science article that has been mentioned can be downloaded free from here: http://sun-valley.stanford.edu/~moishi/science06_roa.pdf

For the chloroplast to have evolved first it must have been lost independantly in every eukaryotic lineage that currently does not contain chloroplasts leaving no trace behind - This scenario is extremely unlikely. In the few eukayotes that have lost mitochondria there are genetic traces - there are no such vestiges of chloroplasts in the vast majority of eukaryotes lacking plastids. Also the chloroplast retains more bacterial DNA and bacterial features than mitochondria again suggestive of a more recent origin. Only if you ignore the features of chloroplasts and mitochondria and parsimony can you argue for chloroplasts first.

A good review on the subject is: 'The Environment and Schizophrenia: The role of Cannabis Use' (pdf) Also remember that Pubmed is your friend.

you might be interested in this this article: Laterality. 2004 Apr;9(2):189-99. Right-left and the scrotum in Greek sculpture. McManus IC. The scrotum in humans is asymmetric, the right testicle being visibly higher than the left in most men. Paradoxically, it is also the case that the right testicle is somewhat larger, rather than smaller, as might be expected. Greek classical and pre-classical art, which took great care in its attention to anatomical detail, correctly portrayed the right testicle as the higher, but then incorrectly portrayed the left testicle as visibly larger. The implication is that the Greeks used a simple mechanical theory, the left testicle being thought to be lower because it was larger and hence more subject to the pull of gravity. The present study examines data on scrotal asymmetry in more detail, and puts them in the context of Greek theories of functional differences between the right side and the left side.

LSD seems to cause different effects in the cell than if the receptor is activated by serotonin. This is probably because the different chemical structures of LSD and serotonin interact with the receptor in different ways and this leads different effects on cells. Similar structures can give rise to quite different effects at the same receptor. It must also be rememerbered that many poisons interact with normal receptors and that doesn't make them safe, or their effects normal. It is probably the case that many drugs have evolved to target particular receptors present in many different organisms. For example nicotine probably evolved as a poison to insects but because our version of the receptor is different nicotine doesn't kill us (immediately) but has a drug type effect. Serotonin Receptor Signaling and Hallucinogenic Drug Action: http://www.heffter.org/review/Review2/chap5.pdf

This may be true (although how could you tell) but there is evidence of local oxic conditions - probably a thin layer of oxygenated water at of near the surface of the sea before atmospheric oxygen began to rise, and before the fisr chloroplasts. It is in such places where early eukaryotes with mitochondria could have evolved. Interestingly several modern organsism have evolved endosymbioses with bacteria and these organisms almost always live near an oxic/anoxic border - it is these conditions rather than just plentiful oxygen that encourage endosymbiosis. There is evidence of local oxic conditions and there were also massive chemical sinks that reacted with oxygen preventing it becoming common in the atmosphere for a long time. I don't think any extinction has been linked just to oxygen - the extinction at the beginning of the cambrian occured at the same time as a rise in oxygen but there was also a massive increase in predators and competitors and i don't think the two can be separated as a cause of that extinction. see: The geological consequences of evolution (free pdf) : http://www.blackwell-synergy.com/links/doi/10.1046%2Fj.1472-4669.2003.00002.x

But there was oxygen before mitochondria evolved - it was produced by bacteria that included the ancestors of chloroplasts - but these bacteria were independant of eukayotic cells and so were not chloroplasts yet. Yes that is almost certainly how mitochondria and chloroplasts evolved.

I think the best answer is that mitochondria came first and by quite a long time. Mitochondria are found in every eukaryote (they have been lost in a few but there are still vestiges) but chloroplasts are found only in a few which suggests that chloroplasts evolved after many groups of eukaryotes had diverged. I suppose chloroplasts could have been lost indipendantly in many groups of eukaryotes but this hypothesis is extremely unlikely. Extant eukaryotes without chloroplasts have no trace of chloroplast genes in their genome which is what you would expect to find if they ever had them. There are a small number organisms like the malaria parasite that have the vestiges of a functional chloroplast (apicoplast) and chloroplast genes in their genome. Chloroplasts have a much larger genome and more bacterial features than mitochondria indicating these have had less time to decay and for the transfer of genes to the nucleus. This indicates chloroplasts are younger than mitochondria.

A recent paper states that the numbers are: "hundred billion (10^11) neurons and several hundred trillion synaptic connections" The storage capacity is said to be 10^20 bits. I think the actual number of connections at any one time is less than the number of atoms in the universe but the potential number of connections is higher than the number atoms in the universe. Capacity limits of information processing in the brain. Marois R, Ivanoff J. Trends Cogn Sci. 2005 Jun;9(6):296-305.

There is also a disproportinately large number of genes on the X chromsome that affect mental function. The X chromsome makes up about 3.7% of the genome but 27% of genetic diseases with mental retardation are X liked: see this paper: X-linked genes and mental functioning. David H. Skuse. Human Molecular Genetics, 2005, Vol. 14, Review Issue 1 "Why should there be such a concentration on this particular chromosome (1)? Zechner et al. (2) suggest that the X-chromosome has been engaged in the development of sexually selected characteristics for at least 300 million years and that natural selection has favoured the development of X-linked genes that are associated with higher cognitive abilities. In particular, males are more likely than females to be influenced by haplotypes that are associated with exceptionally high abilities. For an equivalent reason, they are also more likely to show deficits in mental abilities than females because of the impact of deleterious mutations carried in haploid state. The hypothesis offers an explanation for the higher male variance in many aspects of cognitive performance"

The study of gay sheep does seem to indicate that homosexuality is caused by differences in brain structure. There is a question about how this relates to humans but mammalian brains are fairly similar particularly those ancient systems that control sexual orientation and usually make animals unchangeably straight but make some animals (including humans) gay or asexual. It seems too common to be a purely negative recessive. The trait could be maintained if it was advantageous to the relatives of homosexuals: Evidence for maternally inherited factors favouring male homosexuality and promoting female fecundity Andrea Camperio-Ciani, Francesca Corna1 and Claudio Capiluppi Proc. R. Soc. Lond. B (2004) 271, 2217–2221 The Darwinian paradox of male homosexuality in humans is examined, i.e. if male homosexuality has a genetic component and homosexuals reproduce less than heterosexuals, then why is this trait maintained in the population? In a sample of 98 homosexual and 100 heterosexual men and their relatives (a total of over 4600 individuals), we found that female maternal relatives of homosexuals have higher fecundity than female maternal relatives of heterosexuals and that this difference is not found in female paternal relatives. The study confirms previous reports, in particular that homosexuals have more maternal than paternal male homosexual relatives, that homosexual males are more often later-born than first-born and that they have more older brothers than older sisters. We discuss the findings and their implications for current research on male homosexuality.

So gay sheep are caused by an imbalance in the soul? "This study examined endocrine components of sexual orientation of male sheep. Sexual orientation of adult rams was identified through standardized sexual performance tests. Four rams that copulated with ewes, four rams that never mounted females and copulated with males," Horm Behav 1995 Mar;29(1):31-41 A comparison of LH secretion and brain estradiol receptors in heterosexual and homosexual rams and female sheep. Perkins A, Fitzgerald JA, Moss GE.