Tag Archives: biology

Tissue sampling by piggybacking on vaccination or testing campaigns

Obtaining tissue samples from a large population of healthy individuals is useful for many research and testing applications. Establishing the distribution of genes, transcriptomes, cell distributions and morpologies in a normal population allows comparing clinical laboratory findings to reference values obtained from this baseline. The genetic composition of the population can be used to estimate historical migration patterns in paleoanthropology and selective pressures in evolutionary biology.

Gathering tissue samples from many people is expensive and time-consuming, unless it happens as a byproduct of existing programs. Collecting used vaccination needles or coronavirus nasal swabs that have a few cells attached allows anonymous tissue sampling of almost the entire population. A few cells per person are enough for many analyses in modern biology. Bulk collection of needles or swabs has built-in untraceability of biological material to an individual, which should alleviate privacy concerns and reduce the bureaucratic burden of ethics approvals.

Algae tattooed for doping and oxygen administration

The paper by Qiao et al. (2020) in Science Advances shows that unicellular algae injected near a hypoxic tumour photosynthesise oxygen in the body in response to infrared light with wavelength 660nm that penetrates >4mm into tissues. The oxygen saturation of the tumour rises from 6.2% to 30% in 2 hours after the algae receive a 5-minute laser exposure. The oxygen sensitises the tumour to radiation therapy. No side effects were found from the algae in this or previous research. The performance of the algae stayed the same when these were coated with red blood cell membranes to delay their clearance from the body.

Another application of algae that can produce oxygen in the organism is doping in sports. The algae can be tattooed under skin that is exposed to light containing enough of the wavelengths which the algae use and which can penetrate under the skin. For example, long-distance runners outdoors in warm weather have most of their skin exposed to sunlight, thus have a large surface area suitable for algal oxygen production. The additional oxygen from photosynthesis improves athletic performance. The only question is whether the oxygen generation is quantitatively fast enough to make a difference. In elite sports, every little advantage counts, so athletes are probably willing to use algae tattoos.

The algae are not dangerous even in deep blood vessels and tissues. Eventually the organism clears the algae, but the clearance of foreign particles is slower in the skin than in deep tissues, as evidenced by the persistence of ordinary tattoos. So the algae will last for a daylong competition.

Patients with breathing problems, for example with coronavirus-induced lung inflammation, may also benefit from algae tattooed on a large area of skin which is then illuminated with 660nm light. Such oxygen supplementation reduces the need for mechanical ventilation. Again, the question is the amount of oxygen from a whole-body algal tattoo.

Learning and evolution switch the sign of autocorrelations

Animals are more successful if they learn or evolve to predict locations of food, mates and predators. Prediction of anything relies on correlations over time in the environment. These correlations may be positive or negative. Learning is more difficult if the sign of the correlation switches over time, which occurs in nature due to resource depletion, learning and evolution.

If a herbivore eats a tasty patch of plants or a predator a nest full of eggs, then the next day that food is not there (negative correlation), but the next year at the same time it is probably there again (positive correlation) because the plants regrow from roots or seeds, and if the prey found the nesting spot attractive one year, then other members of the prey species will likely prefer it the next year as well. However, over many generations, if the plants in that location get eaten before dispersing seeds or the young in that nest before breeding, then the prey will either learn or evolve to avoid that location, or go extinct. This makes the autocorrelation negative again on sufficiently long timescales.

Positive correlation is the easiest to learn – just keep doing the same thing and achieve the same successful outcome. Negative correlation is harder, because the absence of success at one time predicts success from the same action at another time, and vice versa. Learning a changing correlation requires a multi-parameter mental model of the superimposed different-frequency oscillations of resource abundance.

There is a tradeoff between exploiting known short-period correlations and experimenting to learn longer-period correlations. There may always be a longer pattern to discover, but finite lifetimes make learning very low-frequency events not worthwhile.

Why princesses and princes are described as attractive

The bards and scribes who recorded events for posterity received their income essentially in the form of tips from the rulers and the rich, so had an incentive to flatter, describing their patrons as more attractive, virtuous, brave, etc than they really were.

In addition to the exaggeration of their actual attractiveness in reports that have reached us, the children of the wealthy probably really were more beautiful than the poor. Richer youth were better fed and cared for, thus had fewer developmental abnormalities (e.g. bent legs from calcium deficiency) and diseases. The poor were malnourished, lived in dirty conditions and were subject to violence, therefore were more likely stunted, stank and had skin diseases, missing teeth and scars. The latter two distinctions in looks have to a lesser extent lasted to the present day, for the same reason.

Attractiveness consists of the visual, audible and olfactory signals of a fit mate (healthy, fertile conspecific), because organisms evolved to consider fit mates attractive. In times when most people were malnourished and diseased, a well fed and healthy rich person would have been much fitter than most, thus a preferred sexual partner for others.

On the other hand, conditional on surviving to adulthood, the poor likely had better immune-related genes, because they were under stronger selection pressure. Poorer people also experienced more infections, thus acquired stronger immunity to more diseases if they survived. Then conditional on equal looks, a person from a poorer background would have been a fitter mate. Also, the ruling class intermarried to keep wealth in the family, so were inbred (hereditary diseases among European royalty are an example consequence). For these two reasons, it is not surprising that the rulers and the rich found some poor people sexually attractive, specifically the outwardly healthiest-appearing among those who reached maturity.

Arranging a virgin birth in a low-tech way

Warning: this Christianity- and Christmas-themed post may offend or disgust. The procedure described is unpleasant for the receiver.

Fertilisation of an egg cell requires sperm to reach it, which does not require breaking the hymen. A thin tube, such as a hollow straw or reed, can be inserted through the small opening in the hymen to pump sperm (obtained via male masturbation) into the vagina. The simplest way to pump the sperm is to suck it into the straw with one’s mouth and then blow it out. Another way is with an enema pump (bulb syringe) that can be constructed with primitive technology: a hollow leather ball glued to a reed using resin, tar or bone glue. The seams of the leather ball can be waterproofed with tar. The ball can be made to spring back into shape after squeezing, e.g. by constructing it with wire hoops or springs inside.

Successful fertilisation with the above method likely requires many attempts, because the probability of pregnancy from unprotected sex during the most fertile part of the menstrual cycle is 30%. Sexual activity causes hormonal changes in the female organism that facilitate fertilisation, which a simple reed insertion probably does not, but it may be possible to create similar hormonal changes with an erotic massage.

The above method can be used to arrange a virgin birth in a primitive society. No miracles are required, although a virgin giving birth may be marketed as miraculous.

Modern in vitro fertilisation technology of course expands the range of ways to engineer a virgin birth.

Sexual signals are similar to money

Ronald Fisher analyzed signalling in biology through traits that do not confer direct fitness advantage (higher survival or fecundity), but are desired by the opposite sex. This attraction is an equilibrium in a coordination game – if a potential mate has traits desired by the opposite sex, then the offspring with that mate are likely to have these traits as well and succeed in attracting the opposite sex. The traits confer a mating advantage, which is part of a fitness advantage, justifying the desirability of the traits.
It is a coordination game, because in a different equilibrium, traits without a direct fitness advantage are not desired. Then these traits do not give a mating advantage to the offspring and therefore do not have an indirect fitness advantage either. Then it is not fitness-enhancing to desire them. In summary, if a trait is expected to be desirable in the future, then it is desirable now, and if a trait is expected to be neutral or undesirable, then it is neutral or undesirable now.
Fiat money is inherently worthless, but in one equilibrium of the money game, has positive value in terms of other goods. If everyone expects that others will accept money in return for goods in the future, then it is useful to obtain money now. So everyone is happy to deliver goods in return for (a sufficient sum of) money now. The money game is a coordination game, because if everyone expects money not to be accepted in the future, then they do not give goods for money now. If money is expected to be worthless, then it is worthless, and if money is expected to be valuable, then it is valuable.
An overview of signalling in biology is at http://en.wikipedia.org/wiki/Signalling_theory and Fisher’s theory at http://en.wikipedia.org/wiki/Fisherian_runaway
The coordination game of money is studied by Kiyotaki and Wright (1989, 1993): http://www.jstor.org/stable/1832197 http://www.jstor.org/stable/2117496 and more simply explained in van der Lecq “Money, coordination and prices” https://books.google.com.au/books?id=r1r40SB0Wn8C&pg=PA29&lpg=PA29&dq=fiat+money+coordination&source=bl&ots=iI0M96m-qz&sig=lRHBAWIXYZs2V5S-iNFeH-2yar8&hl=et&sa=X&ei=d3lqVeneJ8TvmAX4vIGgDg&ved=0CEoQ6AEwBw#v=onepage&q=fiat%20money%20coordination&f=false