Biology Notes

Something I wrote on this controversy, at my other blog:

http://davidcollard.wordpress.com/2013/04/11/do-listen-to-eo-wilson/

Julian O'Dea

Something I wrote at my other blog on human female gestures, Desmond Morris, Manwatching and so on.

http://davidcollard.wordpress.com/2013/04/10/womanwatching-no-1/


Julian O'Dea

I just heard something interesting on Australia's Radio National, late in the afternoon, today being 6 January 2013. In a discussion of unconscious motivation, the speaker claimed that it has been found that people have a tendency to marry people who already share their surname.

I find this interesting because, if true, it would confound one of the classical approaches to assessing inbreeding in human populations. The method, originally invented by Francis Galton in England in the 19th Century, relies on looking for an excess of marriages between people of the same surname, on the assumption that this represents people marrying their cousins of the same name. That is, it is meant to provide a measure of inbreeding.

However, if people have a psychological propensity to marry people with the same surname, without reference to their being relatives, this tends to weaken Galton's classic method, does it not?

Such a confounding effect would presumably have led to a systematic overestimation of levels of inbreeding.

An improbably large amount of work, in many countries and laboratories, has gone into studying a few polymorphisms in the red blood cell biochemistry of sheep. Two of these polymorphisms are the variation in glutathione levels in the red cells of sheep and the variation in red cell potassium levels. The latter has probably attracted most attention, with a great deal of work on the existence and significance of genetic variation that divides flocks of sheep into high potassium (HK) and low potassium (LK) sheep. A lot of this focussed on possible relationships with production characteristics, such as wool quality.

I did my PhD in a blood physiology laboratory at the University of New England, Armidale, New South Wales, Australia. One of my supervisors was Professor JV Evans, who was the man who made the first crucial observations on HK and LK sheep and had a distinguished career as a blood physiologist.  He was an impressive and gifted scientist and a good supervisor.

I didn't work on the HK/LK model, but I did do quite a bit of work on the function of glutathione, the ubiquitous antioxidant tripeptide which helps protect red blood cells against oxidative damage. Among other things, I published a paper reporting that sheep whose red cells had higher levels of glutathione were more able to reduce methaemoglobin, the oxidised form of haemoglobin. I suggested that this might be one reason why some sheep would have high glutathione (GSH) levels. They would help the sheep deal with oxidative stress from plant toxins in the diet leading to effects such as haemolytic anaemia. Haemolytic anaemia is anaemia caused by the breakdown of red blood cells (haemolysis). 

What I want to suggest here is something that may be a new proposal. Namely, that the advantage of low potassium levels in red blood cells may relate to the fact that during a haemolytic attack, with red cells bursting and releasing potassium, the entry of potassium into the bloodstream is dangerous because it can interfere with the normal beating of the heart. Therefore it is reasonable to suggest that LK (low potassium) sheep would be at less risk because a bout of haemolytic anaemia would not result in as much potassium being released into the bloodstream as in the case of HK (high potassium) sheep.

In short, the LK genetic variant, like the high-GSH variant, might be an adaptation to the risk of haemolytic anaemia in flocks of sheep, which are constantly exposed to plant toxins.

It is relevant and interesting that cubozoans (box jellyfish) have recently been reported to exert their very rapid and fatal toxic effect by causing potassium to leak from red blood cells, thereby causing cardiac arrest. And many haemolytic snake venoms also operate in part at least by affecting heart function in a similar way.

I am not aware that the above suggestion for the adaptive function of the LK trait in sheep has been made previously, but I have yet to do a full literature survey. That being said, an immense amount of work has been done on the genetics and significance of the HK/LK trait in sheep red cells, and I cannot recall this suggestion having been made, at least at the time when I was doing red cell biochemistry during my PhD.

With each passing year, it seems that we discover Evolution using physical principles in new and surprising ways. It is clearly dangerous to assume that some kinds of adaptations will not be found in organisms. If it is physically possible, Nature seems happy to do it.

Fortean Times recently (August 2012) had a highly speculative cover article by Scott Deschaine asking if some UFOs are not actually living creatures. I don't think this is the least bit likely, but I was interested in a letter of critique published in the November 2012 issue of the same magazine. Among other things, the writer, Martin Jenkins, writes that an organism floating high in the atmosphere could not rely on a lighter-than-air gas, because hydrogen and helium would be unavailable. And that the alternative of heating its internal air to achieve buoyancy like a hot-air balloon would be prohibitively expensive in terms of energy.

However, Mr Jenkins has forgotten that the following gases are also lighter than air, and are feasible as biological products: carbon monoxide, ammonia and methane. The two latter gases have, in fact, been used to provide lift for balloons. Also, in terms of producing a great deal of heat very quickly, the bombardier beetle can actually produce a boiling liquid to protect itself from predators. I cannot see any necessary objection to an organism producing heat to warm air to help keep itself aloft.

So, neither of these two objections seems strong. This is not to say that I believe we will find large organisms floating high in the atmosphere. But I would not be amazed to read eventually, for example, of an insect using methane or ammonia to help it remain aloft. Insects produce ammonia as a waste product which occurs in the gut.

(I have been wondering if the giant flying insects of the Carboniferous, including the "dragonflies" of the time, could have had a boost from lighter-than-air gases inside their bodies or wings, although the usual explanation given is that the atmosphere of the time contained more oxygen or was denser, both of which would have allowed large insects to fly more easily.)

One further objection to the theoretical existence of large unknown creatures living high in the atmosphere is that we should be able to see them. However there are plenty of animals which are largely transparent.

I suspect one of the stronger objections to Deschaine's speculations is that we do not observe the detritus of unknown organisms raining down on us, in an analogous way to the constant deposition of organic material on the sea bed.

Some time ago, I wrote a post on the possibility that the low ultraviolet light in rainforests, such as that I once measured in North Queensland, might contribute to rainforests being "hot zones" for disease organisms.

I want to raise a few more points here, and I shall flesh out this post over time. The points relate to the role of UV light in the ecology of microbes and other organisms. I want to touch on microbes in clouds; UV levels in clouds; the role of low UV in seasonality of ailments due to bacteria and viruses, such as respiratory illness; the role of UV in creating microenvironments in forests (for example, the work of Frances Haines, Barbara Han and myself in measuring UV light in rainforests); the importance of UV to frogs and reptiles; and the penetrance of UV into bodies of water.

My earlier thoughts on the evolution of sex are given here:

 http://julianodea.blogspot.com.au/2005/12/odea-j.html

and here:

 http://julianodea.blogspot.com.au/2011/11/selfish-chromosome-why-sex-evolved-by.html.

They have been cited by Glansdorff et al. in the Journal of Molecular Evolution in 2009, here:

 http://link.springer.com/article/10.1007/s00239-009-9277-7/fulltext.html;

and are mentioned in the Wikipedia article on intragenomic conflict:

http://en.wikipedia.org/wiki/Intragenomic_conflict#Evolution_of_sex

Further thinking has led me to take a broader perspective on the problem, and I shall gradually add more material to this post. The main point remains: that sex evolved because it is to the advantage of the genetic material itself. This is because the genetic material is able to recombine into desirable new combinations in offspring that proliferate well, thereby favouring the genetic material itself.

Sex provides continual improvement in the genetic makeup of organisms. Unlike the genetic material in asexual organisms; which will have no such way of entering new, more effective combinations; genetic material in sexual organisms will be able to recombine into more efficient and adaptive combinations. Individual organisms containing such effective combinations will proliferate well and the genetic material they contain will tend to dominate the next generation. In short, genetic material that codes for sex will proliferate more effectively than genetic material that does not.

Most theories on why sex evolved discuss sex in terms of its advantage to the individual organism or to the population. My approach focusses on the advantage to the genetic material itself in coding for sex.

Sex provides opportunities for all the chromosomes or genetic elements to form new combinations with other genetic elements which may a) combine better to produce a more effective genetic makeup for the carrier organism and b) introduce new, more adaptive mutations and c) allow less effective traits to be ameliorated by combination with traits that make up for the defect. In some cases, which I have already discussed previously, genetic elements which are seriously defective are effectively expunged by the sexual process.