Seems like it's still contentious, but since avian sex regulation appears likely to be dependent on having two copies of the Z chromosome to induce maleness, the W chromosome that females have is likely to be analogously expendable to the Y chromosomes - so you would see the same patterns just with the sexes flipped?

https://pubmed.ncbi.nlm.nih.gov/28911174/

>in humans, all babies start off development as females.

I've seen this said a few times, and I'm always curious why the common early development pathway is considered female rather than ungendered?

It doesn't seem like enough to say that it requires activation of masculinising hormones to start being male, since presumably there are any number of hormonal triggers required on either path to spur development

In part because 'brown' is a huge range of colours. Everything from dark red to dark green will be called 'brown' if it isn't highly colour saturated. Just about the only colour that won't be is blue, which is a fairly rare pigment in nature

If this were in a scientific publication where seeing the actual numbers in each year was important, I might agree. But this is a data visualisation purporting to show the trend in costs over 5 years, and it is failing to show the main trend clearly. It's the difference between 'showing the data' and 'showing the story'

Man this is terrible. The log scale completely distorts the trend - essentially costs fell by a factor of 100 between 2017 and 2018, and the rest is trivial

Welcome to one of the most hotly debated topics in palaeontology. Feathers, hair, skin, etc rarely survive as fossils, so evidence is sparse. Some people will argue that keratin filaments (not really modern feathers, but more like single strands of fiber that later developed into feathers in some species) are a basal feature of dinosaurs, and so potentially all of them could have been 'feathered' at least on parts of their body, or at certain stages in their life. Others will argue that this feature has developed multiple times, and that features actually related to feathers are restricted to a fairly small group of dinosaurs

Just about all you can conclusively say is that some families were predominantly covered in feathers, and others were predominantly covered in scaly hide similar to reptiles (sidenote: reptile doesn't really have a scientific meaning, as any formal definition would probably have to include birds as well)

Doesn't that mean that whichever layer is added last will dominate?

I'd quite like to see this as a stream graph, maybe using a rolling average. Is the data available somewhere?

Interestingly, there is a paper which suggests that at least some groups of Neanderthals had their y chromosome and mitochondrial DNA replaced via an earlier admixture with modern humans https://www.science.org/doi/epdf/10.1126/science.abb6460

This goes against the theory that ms-fn hybrids didn't happen, and suggests instead that they were selected against in modern humans populations

Just found this: https://www.mdpi.com/2075-1729/12/9/1442/pdf

Which suggests that the host specificity in mammalian lice is due to less opportunity for host switching (relative to birds), and closer interaction with the immune system putting them into an evolutionary arms race which requires specialisation

"Birds, mammals, and their lice diversified over similar timescales, with major lineages diversifying around the K–Pg boundary [21], so it seems that there may be fundamental biological or ecological differences between the lice hosted by birds and mammals that could explain these differences. In general, birds have higher dispersal capabilities than mammals, and this dispersal may provide more opportunities for host-switching [33]. The sedentary and asocial nature of pocket gophers, for example, has been used to explain the high level of host-specificity and cospeciation in their lice [5]. Another major difference is that avian feather lice have little interaction with the host immune system because they mainly consume feathers, which are inert, while mammalian lice consume blood or sebum and directly interact with the host immune system [61,62]. This interaction in mammal lice may lead to an evolutionary arms race and more coadaptation between mammals and their lice, making host-switching more difficult."

There's not much selective pressure on royalty though - rather the opposite

What about prions? Reproduction of a sort with no genetic material necessary