demost

Karma: 12

demost 30 Sep 2023 19:57 UTC
4 points
0
on: The Talk: a brief explanation of sexual dimorphism
Fun fact: in the field of optimization there are heuristics which are modeled after evolutionary principles. These “evolutionary algorithms” also work with populations, offspring generation through mutation and mating, selective pressure, diversity preservation, and so on.
As a rule of thumb, these algorithms also work better when sexual reproduction is used. For example, a standard theoretical benchmark are monotone functions on bit-strings, where each gene takes only two values zero and one, and flipping a zero into a one gives higher fitness in all situations and environments. This seems like an easy situation to optimize, but asexual algorithm don’t find the optimum (where all genes are one) for exponential time (in the number n of genes) if the mutation rate is large. Algorithms which use mating have no trouble. This comes from Muller’s ratchet. [1]
More remarkably, even if the mutation rate is arbitrarily small, asexual algorithms don’t find the optimum for exponential time if they use populations, where in each round they produce a new offspring and prune the least fit individual. Again, algorithms with mating don’t have these problems. This also comes from a version of Muller’s ratchet, but on population level. Essentially, if there is a beneficial mutation then other mutations have time to accumulate until the beneficial mutation has taken over the whole population, and this takes long enough to accumulate very many bad mutations, even for extremely low mutation rates. [2]
[1] https://link.springer.com/chapter/10.1007/978-3-319-99259-4_1
[2] https://www.sciencedirect.com/science/article/abs/pii/S030439752100178X
(free preprints available on arxiv)

demost 3 Dec 2021 16:48 UTC
2 points
on: Omicron Post #3
Researcher Alex Sigal has followed the mutations of the coronavirus in an HIV patient over months [1], and he believes that the pattern of mutation in the Omicron variant is similar to what they had observed in that patient. So he favors the HIV scenario for the development of Omicron.
And he speculates that, given this scenario, this would increase the chances of Omicron being milder than other variants, because, as he puts it, a virus that persists for months in an immunodeficient patient is probably not particularly deadly.
It doesn’t quite match my own intuition, since the major damage of a corona infection seems to come from your own immune response, rather than directly from the virus. But my expertise is quite limited, so I trust Sigal’s gut feeling on this question much more than my own. However, I think that “gut feeling” and “speculation” does describe the level of confidence.
[1] https://www.eurekalert.org/news-releases/609570 (edit: corrected link)
(All infos from German magazine SPIEGEL, which is unfortunately paywalled and in German.)

demost 16 Oct 2021 18:59 UTC
3 points
in reply to: cistrane’s comment on: Covid 10/14: Less Long Cvoid
I don’t think it’s clear that mRNA flu vaccines will be as effective as mRNA corona vaccines.
One reason why SARS-CoV2 is an “easy” target for vaccine is that it has a very low mutation rate (as do other corona viruses). Influenza viruses evolve much faster. A standard problem of flu shots is that they are not designed against the virus that circulates in the winter, but rather against viruses that circulated half a year ago. For the corona virus, this does not make a big difference, but for flu viruses, it can render the vaccine (partially) useless.
The mRNA technology has some advantages because the cycle of development and production is shorter. But it is still long enough that the problem does not go away completely. We should not expect mRNA flu vaccines to be as effective as mRNA corona vaccines.

demost 20 Feb 2021 20:57 UTC
7 points
on: Swiss Political System: More than You ever Wanted to Know (I.)
What a great post! This is really accurate.
Let me add a nuance about the political debate by comparing Germany and Switzerland.
I have moved from Germany to Switzerland (Zurich) 10 years ago. Germany and Switzerland are often considered similar by outsiders, or at least by Germans. To some extent this is true, but from the beginning I was really shocked by how much better the Swiss political system works than the German one (which is already considered sober and highly functional).
The most obvious difference is how much media and news in Switzerland focus on topics instead of people. The typical news headline in Germany is “politician X says that idea Y is bad”. Such articles usually go a lot into detail on who else favors or rejects idea Y, but they usually don’t discuss the advantages and disadvantages of idea Y.
In Switzerland, the news are really different. The headlines still say which institutions (like political parties, cantons, governments, associations; muss less often people) favor or disfavor an idea. But it usually also gives their reasoning. Honestly, I had (and still have) the impression that “20 Minuten” (a free tram tabloid in Switzerland) does this much more often than “Der SPIEGEL” (one of the most renowned German political magazines).
In terms of voting, this makes a big difference. In Germany, voters vote for or against politicians. I had enough discussions in my family to know that they vote “for Merkel” or “for Scholz” (candidate for chancellor by social democrats in German elections), and they do this because they think that Merkel is better than Scholz (or just like her better), or vice versa. I think this is typical for most countries. And I think is a really stupid basis for decision, because over decades Germans have consistently been in the lucky situation to decide between two (or more) competent and sane politicians. So political agendas should make the difference, but they play a rather minor role. In Switzerland, the situation is very different. Even at election day, people vote mostly for parties and their programs (and not for people), and even more so in referenda.
This post describes very nicely where this comes from, and I have little to add. The sheer amount of political involvement and in-depth discussion, the institutionalised exposure to the arguments from both sides (the official voting booklets, but also lots of pro- and contra advertisement), the necessity to form an opinion… You have described it much better than I ever could. Having lived in both countries, I have the strong opinion that political decisions in Switzerland are much better than in Germany. I would recommend every other country to adopt the Swiss system if I only had the slightest idea how to do that. Unfortunately, I don’t believe that “copy the set of rules” would work, because it leaves out the grown political culture. But at least your post gives me a better understanding of why it works, so thank you for that!