CharonY

There is even more to it. You need basically a kind of cellular environment for it to its proper thing. You can (to some extent) throw together RNA, ribosomes, enzymes, amino acids and the proper buffer together to produce proteins, but those would not do much. They need other proteins, all kind of metabolites membranes etc. to sustain function. So it is exactly right that we actually need functional cells to actually do something.

Exactly.

Absolutely. The problem with these types of questions is that they are very difficult to test. Therefore, narratives alone are pretty much worthless, which is why folks advocating thermoregulation created some models to check whether they make sense (and there has been some back and forth). But as always, the situation is highly multifactorial and a lot of things can play a role, including stochastic effects (e.g. drift) or something that occurred during that time, but for which we won't find any fossil evidence for. For example, one could speculate that at some point there was some extremely severe skin disease or parasite where somehow loss of functional hair provided a benefit. We cannot prove it either way, but clearly it does require some level of substantiation. Similarly, sexual selection has been mentioned by some, but as these also do not leave records, it is not a terrible useful model.

So based on your hypothesis, the orangutans who are able to shield themselves form rain would soon be naked? Each species history is unique and comparisons would only make sense if we find equivalency in critical aspects. One argument for heat sensitivity of humans is that the human brain is quite large and is very sensitive to overheating. Quite a few animals have for example a carotid rete, which helps cooling the brain especially during bursts of activity. We don't have that, for example. And I will again point to folks living in savannas who often only cover their lower body parts and somehow are still alive. Many animals in that habitat reduce activity during the day or have some other physiological adaptations to deal with heat.

External parasites are indeed one of the hypotheses. Another one is sexual selection. The others have been previously mentioned. By taking into account where our ancestors (australopiths) lived it was suggested that heat load reduction is more important when foraging in tropical habitats. There is also a suggestion that bipedalism evolved because of thermoregulatory benefits (https://doi.org/10.1016/j.jhevol.2016.02.006). These were more important to our ancestors as they moved from forest environments into more open habitats. Conversely it would mean that clothing likely only became more relevant when moving out of tropical climate zones. There are a range of suggestions on what behavioral adaptations might have occurred to protect from cold, but they appear to be fairly minor, especially concerning our physiological abilities to deal with heat. So far the strongest evidence we have point toward thermoregulation as one of the major influences.

That is a good question and which is why it is necessary to gather information, such as - what is the timeline of hair loss? Was it rapid, or gradual? - how much fitness loss is associated with a given loss? - what kind of protection was feasible at any given point in human development (in terms of tool use and needs, hunting behaviour etc.) and how much of it could it offset the above fittness loss? - what are the benefits of mutations? If it requires so much effort to counteract its negative effects, why did it became dominant in the first place? Again, coming into a situation where certain traits are not needed does not make them magically disappear. As noted, the evidence so far to not seem to support the development of clothing before hair loss. I.e. hypotheses need to conform with existing knowledge. In that regard, persistence hunting was one of the hypotheses that tried to explain benefits of hair loss. I will also note that tentative evidence for man-made fires seem to predate tentative evidence for man-made clothing. Also, I note that the San people referenced earlier often wear very little clothing (up to somewhat recently) so it certainly does not seem to be that detrimental in climates where our ancestors lived.

I think the issue is that it is very easy to make some sort of grand hypothesis in terms of evolution just by conjuring a scenario that somehow provides some kind of selective pressures that seemingly make sense. Things like the aquatic ape hypothesis are rightly criticized because of those. So if we think that we can come up with something better, at lease some level of evidence should be provided that whatever we come up with is in line with what we know (or at least have some sort of evidence). Fundamentally I find narratives that some species did this and this is why the lost a particular genetic trait problematic, as it conjures the idea that once a species did a thing, it resulted in genetic changes. The reality is the opposite of course. Mutations for hair loss occurred, likely somewhat frequently, but their frequency only increased when they either were not detrimental or became under positive selection. I was typing the comments below, when I noticed that joigus provided a similar reference so I am just keeping it brief and just state that the timeline when changes in hair patterns happened predated any evidence of potential tools that could be used for making some sort of warming clothes. So things like simple shelters or rain protection obviously had low impact on those mutations as all our relatives are still fairly hairy. But what the drivers are to keep hair loss around is still up to debate and as joigus pointed out, far from resolved.

It is a bit funny to start with valid criticism, but then falling into the pit of, well, making things up. For example, if loss of hair was due to the wearing skin cloaks, then why did our presumably hairy ancestors start with that practice in the first place? How would they prepare skins to wear and is there any evidence to that end? I doubt that they would just wrap themselves in putrefying carcass (at least non of our cousins are doing it).

I am not sure whether I understood the instructions, but I am licking coffee from the whiteboard now.

You have to look out for migrating cells with flip charts. They are almost impossible to get rid of and cause inflammation responses everywhere.

May I interest you in de-differentiation? A process where a differentiated cell decides to try something new and becomes a state that has higher flexibility and then changes again to a new job- but slightly different then those that differentiated directly into the role? I assume it is a process exclusively developed to annoy the heck out of cell biologists.

It should also be noted that at least in US Colleges can only use factors such as race in admission only in a fairly limited sense. Specifically, they are only allowed to use it in order to create a diverse learning environment. While it can (and hopefully) does help underprivileged groups, I *think* they are not allowed to use that as justification. While only tangentially relevant, it should also be added that a minority of colleges use such mechanisms and it is banned in a few states for quite a while already. At the same time, if you ask folks some think that this is a dominant selection mechanism. I.e. similar to other efforts of equity, folks overestimate what is actual done (i.e. the level of course correction) relative to what is actually happening. And certain news outlets heavily use the assumed impact and treat it as reality to manufacture outrage. Edit: I should add that there is apparently a playbook/script of sorts by conservative groups that try to associate e.g. critical race theory and affirmative action with racism, gender identity to sexual exploitation/grooming and so on. While this was the purview of the extreme fringe, they have gotten sufficient traction that they have entered the mainstream (as evidenced by politicians espousing such rhetoric). So it is not just shitty reporting, as my post might have suggested.

Well, authors are often very busy and most are unlikely to answer anything that can be (mis)construed as medical advice of any sorts. Complicated open ended questions are also less likely to be answered.

In human fossils significant bran growth was seen around 2 million years ago. While cooking would be difficult to pinpoint as the relevant factor, a study in 2004 (Stedman, H., Kozyak, B., Nelson, A. et al. Myosin gene mutation correlates with anatomical changes in the human lineage. Nature 428, 415–418 (2004) https://doi.org/10.1038/nature0235) has found a mutation in a gene that leads to weaker jaw muscles, estimated to have occurred about 2.4 million years ago. In related primates, the jaw muscles are connected to large skull crests, which are absent from modern humans. Thus, the author speculate that when our jaw muscles stopped putting stress on the skull, the crests were not important anymore and might have opened the way to further skull growth. However, it has also been argued that some fossils still showed small brain sizes as recent as 1.8 million years ago (early Homo erectus). Now I don't know much about the consensus in terms of first fire use, but using wiki a range of 1.7 - 2 million years ago are mentioned. While the evidence from that time does not seem definite, it would line up with the fossil data for brain growth and myosin gene mutation. It does appear that fire use 1 million years ago is rather certain, so if we used this time point the largest discrepancy between fire use and brain growth would be around 1 million years ago (though certainly not millions). I have also read that folks speculate that beyond cooking meat, the simple act of pre-processing food (e.g. mashing and cutting) could have contributed to the lack of need of large jaw muscles and such tools were around since at least 2.6 million years.

Of course there are dozens of grifters waiting to take his spot, though.

I think that is something that many folks underestimate.

In addition, the gastrointestinal system for herbivores often is often complex and have sophisticated systems to extract nutrients efficiently (e.g. longer intestines, multiple stomachs), which require more space, too. Different belly size within a species are obviously caused by different reasons.

Actually all our publications disclose our affiliation and (professional) contact information. I have occasionally answered seemingly honest requests and questions from the public (especially during the pandemic) and/or directed them to relevant health professionals, as time allows. I think in the age of social media things might have gotten worse in some hot-button issues and some colleagues have indeed gotten death threats. However, this is more commonly because they were giving interviews and/or were active on social media and not because because of publications, as these are rarely read by folks who bother to send out threats.

Being on the receiving end of this question a fair bit, I think the issue is not the question "Where are you from?" It is generally only an issue if the follow-up is "no, where are you really from".

One factor is that similarly to other hot topics like immigration, politics likes to seize on such rather complex questions in order to gain cheap points. Rather quickly these issues then become rallying points and are not discussed in sufficient depth anymore. It is also funny to me that some folks argue that all that wokeness is finally causing backlash- whereas in fact the term is in itself a backlash to a status quo where systemic injustice was considered the norm and justified. The blame for inequality was then squarely placed on certain, typically powerless groups. I mean, in this thread there are a couple of important steps such as "hey hold on, how do we define woke in the first place?". Even such simple things are often not addressed in what passes as public discourse nowadays. Edit: I feel like I should start embracing old man attitude and hypocritically blame social media for all failings of modern society. While writing a post on social media.

I also disagree with the premise and the comparison with modern telecommunication. The development of the latter was not so much breakthrough, but rather incremental developments of a range of different related technologies. And while it has influence on the society (in positive and negative ways) and especially on habits, I am not so sure about what the "breakthrough" really would be. It had a higher impact on lower-income countries, where cell phones put a computer into almost everyone's reach. But elsewhere I am not that sure what the breakthrough really is, other than convenience and more distraction (yes, I am getting old). So as such I do no think that the technology has actually "solved" much and I am not sure whether that would be the correct or fair way to look at medical progress either. On the medical side of things, breakthrough developments were many, with vaccines for each new disease pretty much on top of the list, as each new effective vaccine radically changes the way we can manage a given infectious disease. Better and safer anesthetics has revolutionized what can be done in surgical practice. Antibiotics were breakthrough developments and we might live to see what happens if they don't work anymore. Insulin is not a cure and not sexy, but just imagine a world without it. I think the impact would be much more immediate than the need to use a landline. Even mundane things such as better health recording system, screening and so on that improves our everyday health so in that regard I do think that the focus on shiny things that we call breakthrough can be a bit misguided, at least when it comes to population-wide impact. Well, pneumonia can be a pretty bad way to go, depending on its form, not to mention that one might spread pathogens. I have quite a few more items on my list that I'd prefer over pneumonia.

Hold on, you can close browsers?

A unicorn does not have arms, so would be disqualified on a technicality? Edit: harms/arms need coffee

I guess it means that one of your premises is going to turn out wrong (depending on your definition of fully closing, probably).

Probably dropped like a fly.