Ancestor of animals identified in Australian fossils | Hacker News Reader

Ancestor of animals identified in Australian fossils

phys.org

106 pointsguybedo38 comments

I find it amazing that we all start from a ring that turns into a tube and then it bends and twists into a complex being.

Interesting part is that ring is the anus. The first organ that gets formed is the anus.

It also seems that during development, we pass through various stages, as if the organs of higher order life forms are a series of hacks added on top of the prior ones.

This is the well-known fallacy known as "ontogeny recapitulates phylogeny".

https://en.wikipedia.org/w/index.php?title=Ontogeny_recapitu...

No actually it's not a fallacy, taken from your own link:

"Embryos do reflect the course of evolution"

Try quoting more than the first half of a sentence intended to placate people who learned to believe in the fallacy.

the shortcomings of the theory had been recognized by the early 20th century, and it had been relegated to "biological mythology" by the mid-20th century

The Haeckelian form of recapitulation theory is considered defunct.

the Biogenetic Law was abandoned, and its fall freed scientists to appreciate the full range of embryonic changes that evolution can produce

The cited book is 1963. I'd feel more comfortable with something more recent. It seems to be a debate of degree. Earlier forms do tend to be preserved in the embryo, but it's only a tendency, not a "rule".

Mentioned in my other comment above: https://en.wikipedia.org/wiki/Ontogeny_and_Phylogeny_(book)

>> it had been relegated to "biological mythology" by the mid-20th century

> The cited book is [from] 1963.

Sorry, when would you expect a citation for "it had been relegated to 'biological mythology' by the mid-20th century" to date from?

As a hard and fast rule, yes, it has been deprecated, but not as a tendency or influence.

AFAICT the comment you first responded to is consistent with the modern form of the idea. There's no reason to assume they were specifically thinking of Haeckellian recapitulation.

It is a fact that many embryos go through stages similar to portions of that organism's evolutionary history. This fact alone justifies the cautious phrasing of the great-grandparents comment, in my opinion. Since this fact is also indicated in the excerpted quote you criticize, I think the quote served it purpose. (Though I would agree the 'reflect' can be misinterpreted).

This idea is explored heavily by Steven J. Gould in his book Ontogeny and Phylogeny. I highly recommend anyone interested in this idea to check it out. As far as I remember the "fallacy" is not that these stages exist, but that evolution works by adding new stages on top and pushing the previous stages down into development.

Surely that is one of the ways evolution works?

There is a difference between (a) observing what happens for some organisms, and then saying it is "as if" X were the case, and (b) asserting that X must necessarily be the case.

The parent comment is similar to the fallacy you mention, but as phrased is not an endorsement nor assertion of the fallacy.

I don’t know much weight to put on “seems” but the view described is considered biological mythology. https://en.m.wikipedia.org/wiki/Recapitulation_theory

It's not completely, wrong, as described in the "Modern Status" section in your link. IIRC human embryos have gill-like structures for a little bit.

Anybody remember the end of Waterworld?

I suppose the first improvement to a tube that eats would be to hold the food in a bit longer, for more complete digestion. This is especially true if you already have some coercing mechanism in place to flow/keep food into the mouth hole, even if that's clogging the front end with forward movement.

It's not only the anus, the body has the topology of a donut (plus some extra holes):

https://www.youtube.com/watch?v=egEraZP9yXQ

"The body is not a doughnut, it's a XXXX holed doughnut"

Amazing video, thanks for sharing. The concepts he explains to get to the conclusion are awesome. The kinds of things that have bounced around ones head while on psychedelics, while lacking the question, let alone any answers.

Re: The first organ that gets formed is the anus.

And some modern day ancestors stay that way into adult form (or at least externally adult in appearance).

On a serious note, it looks roughly slug-like. Most guesses of the earliest animal were more "wormy", that is, narrow. It's also odd that Spriggina and Dickinsonia left no ancestors (that we know of). The "earliest mover advantage" does not always play out. They are akin to the Apple Newton of smart-phones/PDA's. (Plus, having naughty-part sounding names probably didn't help).

I suspect Spriggina and Dickinsonia were single-celled organisms. (Even today thumb-sized semi-mobile cells exist.) That gave them an early advantage when oxygen first became plentiful because they didn't have to coordinate millions of cells, but rather merely grow bigger. However, multi-cellular eventually caught up and had scalability/complexity advantages over one-big-cell. The digestive track may be such a result. Spriggina and Dickinsonia probably more or less just sat on stuff and slowly digested it in place. The new system allowed Jabba the Mini-Hutt to eat on the go, useful as predation increased or for food sources too small to bother sitting on.

We see similar patterns in social animals and symbiosis in general, such as flowering plants. They are slower to appear on the evolutionary stage, but eventually out-compete creatures that rely on simpler behavior. Neanderthals had bigger brains, but were probably less social. Trade and sharing ideas gave us more tools and food sources. After the "Dino Asteroid", birds had the early predator advantage and grew quite large and fierce. However, the social pack hunting of mammals eventually gave them the edge.

For vertebrates, yes. Not all animals

https://en.wikipedia.org/wiki/Protostome

Thank you. I learned something new today!

Not all make the anus first.[0]

> The key difference between Protostomes and Deuterostomes is that in protostomes blastopore becomes the mouth while in deuterostomes it becomes the anus.

But yes, for humans it's the anus ;)

0) https://www.differencebetween.com/difference-between-protost...

We are still just tubes, like a lot of other animals. One long tube from our mouth to our butt, with a lot of crazy stuff on the outside.

I had to check because I was skeptical, but Bilateria actually does include the radially symmetrical echinoderms, i.e. sea stars, urchins, and other weirder creatures. They go through a bilaterally symmetric larval stage.

It's pretty interesting that a starfish is more closely related to us than it is to, say, an octopus or a crab.

Link to journal article this article is based on[1].

[1]https://www.pnas.org/content/early/2020/03/17/2001045117

My sci-fi fantasy consists of building such an ancestral organism by modern genetic technologies and phylogenetic simulations to come up with a likely ancestral genome that would actually work. Some kind of Jurassic Park for the evolutionary biologists.

I was installing Ubuntu 19 today and thinking not bad Ubuntu has lasted 19 releases.

Meanwhile this thing has been producing new releases and updates for 550 million years.

Ubuntu's version numbers are year.month. So "Ubuntu 19" means it's of the 2019 vintage.

To add to the correction, there is no "Ubuntu 19" really, as all the versions have year.month as you mentioned. So "Ubuntu 19.04" and "Ubuntu 19.10" are the only versions that exists.

I think this thing was deprecated soon after release, and its userbase migrated to something more suitable.

BTW, Ubuntu 19.x is its 30th/31st release: https://en.wikipedia.org/wiki/Ubuntu_version_history

Opening paragraph: "A team led by UC Riverside geologists has discovered the first ancestor on the family tree that contains most familiar animals today, including humans."

most <> all

Ok, we've taken 'all' out of the title above.

Now it's lost all meaning. :(

Why not say "ancestor of [most] animals" or similar?

I would say that's implied.

Wow, it is amazing to know that as years passby people tend to discover interesting stuff from the past.

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