On a grander scale, the biological history of life itself weaves the career of the human race into a context of profound interconnectivity.
It's natural to contemplate your origins, the place and culture you come from, your ancestors and the history of your family. It's even more profound to contemplate your biological origins, your ancestry into species unrecognizable from your own.
It really is a humbling experience to trace a path thousands and even millions of years into the past. The end result is an increased appreciation for the beauty of nature and for the inseparable unity of the human race.
Be awed by the beauty but also be wary of the horror that is existence.
Awe, beauty and horror are human concepts. Do not let that bias cloud your logic. When something is beautiful to you, you become blind to the horror. When something is horrible to you, you become blind to the beauty. Best way to view something, is to ignore both, and judge it dispassionately.
Nothing is beautiful, nothing is horrible. That is true understanding.
If there were Schema.org/Animal and/or schema:AnimalInstance classes, what do you list under a :breed property to indicate that e.g. one parent is breed X and another is breed Y?! That's definitely not a DAG; that looks like a feature clustering dendrogram.
DNA barcoding > Mismatches between conventional (morphological) and barcode based identification https://en.wikipedia.org/wiki/DNA_barcoding#Mismatches_betwe...
Taxonomy (biology) https://en.wikipedia.org/wiki/Taxonomy_(biology)
FWIU, there's at least one DNA-based organism naming system; IDK how much that helps resolve :Animal and :AnimalInstance if at all?
Flight is so useful, it evolved 4 times independently. With very similar solutions. https://en.wikipedia.org/wiki/Flying_and_gliding_animals
And crustaceans keep evolving into crabs. https://www.popsci.com/story/animals/why-everything-becomes-...
And who even knows how many different times high level intelligence has evolved. I think octopi, birds, and mammals are all good examples of separate intelligence tracks with similar results.
I'm not a biologist, but I found this paper (Podani, 2019) about the "Coral of Life" metaphor interesting: https://link.springer.com/content/pdf/10.1007/s11692-019-094...
The corals were particularly memorable. My dad's also from a comp sci background, and noticed how the coral colours are RGB.
From other HN posts, I'd been thinking about the Tree of Life, and wondering about roots. Trees are basically mirrored around ground level. But coral grow without roots!
So yes, I like the "Coral of Life" metaphor. It fits well with the Big Bang model, of having a single starting point and growing from there.
Things get tricky when you talk about species, because species are (arbitrary?) equivalency classes of individuals.
To summarize the article (using a more familiar animal):
Polar Bears and Grizzly Bears are different species… Yet they can reproduce! Good god, that means they were once the same species, then different species, and now the same species again! My minds blown!
Silly…
In this sense a cycle can’t occur because a branch would need to reach back in time and rejoin with an ancestral branch. It would be a different kind of grandfather paradox: who would be the ancestor and who the descendant in a cycle?
Maybe someone could help point out the flaws in this model.
what's surprising is that it took so long to realize that.
we only need to look at dogs to see an immense variety that is still interbreedable.
and if dogs can, why not sharks or bears?
i think the only reason we don't don't see that more often is because they each live in different habitats and opportunities for interbreeding are rare.
i expect genetics will be able to give a better answer as to how much variety is needed before interbreeding no longer works.
In general, the babies that are born have already passed through a nightmarishly difficult biological gauntlet to survive. If they fail at any stage, the pregnancy is simply terminated. The majority of fertilizations never lead to births as a result.
You can’t gradually go from one to the other.
Absent some mechanism we don’t know about, conception simply doesn’t work when the sperm and eggs have different numbers of chromosomes.
To be clear, the concept of chromosome isn’t as objective as one might think… nevertheless, it’s an example of the type of genetic difference that simply precludes reproduction.
The pertinent question remains: at the molecular level, how?
I don't think we're disagreeing here, just simplifying like all conversations about biology.
Species are sent back and forth between those two extremes by changes in the environment brought on by our planet's constantly changing climate, topography and ecosystems. Sometimes, when the isolation ends, the combination of made-permanent recessive traits turns out to be harmful and the isolated population is replaced by the larger one (if the larger one survived), and other times it is helpful and they spread out into the larger environment. It isn't a contradiction any more than first and second gear on your bike are - you can't have them both at once, but they are switched between by systems external to the bike itself (the rider).
The idea is that every species is descendant from a highly inbred population of another species. Curiously, this happens in the Bible (Noah's ark).
The molecular basis is the same as that of Darwinian evolution (transcription errors plus whole-organism natural selection), combined with the usual laws of population genetics.