
World's first animal was a pancake-shaped ocean dweller - okket
https://www.nature.com/articles/d41586-018-06767-6
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mesozoic
Oldest known* not first. If this was the first then you're saying there was a
major jump from single cellular to billions of cellular animals. Oh accuracy
of headlines...

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ddoolin
Would you call single-celled organisms (or anything that came before
Dickinsonia) animals?

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baddox
As far as I know, Animalia currently only includes multicellular organisms by
definition, but maybe different definitions are used for the distant past.

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a1369209993
I don't know about the definition you're using, but _taxonomically_ speaking
there is at least one single-celled organism that's _indisputably_ part of (as
in descended from) Animalia: Canis lupus incertae sedis[1][2], a infectious
disease that evolved from dogs[3]. (On further wiki-walking, there also appear
to be similar diseases evolved from devils, hamsters, and clams[4].)

There are also choanoflagellates[5], which might have reverted to single-
celled life after a stint as multicellular, or might not, but are in any case
more closely related than the opisthokont[6] common ancestor of animals and
fungi. (These are rather more relevant to the context of "were there single-
celled animal ancestors?". If opisthokonts already formed differentiated
clonal colonies, then there was no point in the main [modern normal animals]
lineage that was defensibly already animal but not yet multicellular.
Apoikozoa[7] allegedly formed colonies, but it's not clear to what extent they
were differentiated and/or obligate.)

1:
[https://en.wikipedia.org/wiki/Canine_transmissible_venereal_...](https://en.wikipedia.org/wiki/Canine_transmissible_venereal_tumor)

2: [https://www.quora.com/Has-a-complex-organism-like-a-dog-
ever...](https://www.quora.com/Has-a-complex-organism-like-a-dog-ever-evolved-
into-a-single-cell-organism/answer/Israel-Ramirez)

3: [https://sci-hub.se/https://doi.org/10.1016/j.gde.2015.03.005](https://sci-
hub.se/https://doi.org/10.1016/j.gde.2015.03.005)

4:
[https://en.wikipedia.org/wiki/Transmissible_cancer](https://en.wikipedia.org/wiki/Transmissible_cancer)

5:
[https://en.wikipedia.org/wiki/Choanoflagellata](https://en.wikipedia.org/wiki/Choanoflagellata)

6:
[https://en.wikipedia.org/wiki/Opisthokonta](https://en.wikipedia.org/wiki/Opisthokonta)

7:
[https://en.wikipedia.org/wiki/Apoikozoa](https://en.wikipedia.org/wiki/Apoikozoa)

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maxxxxx
I wonder if one day we will have technology that does a comprehensive scan for
fossils without having to dig them up. Right now it's surprising that they
find anything considering how manual and hit and miss the process is. i can't
even imagine how much good stuff we will never find with current methods.

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drumttocs8
Oldest discovered != first

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nvahalik
Yep. Since it is unable to be observed it cannot be proven.

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mikestew
Wouldn't the world's first animal be prehistoric by default? I mean, I assume
the priority of any first animal on any planet is not going to be scribbling
things down for posterity.

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jetrink
If we allow that humans and other extant creatures are not prehistoric, then
it is possible (though not at all likely) that the first animal is one that is
still with us and therefore not prehistoric.

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skj
Some humans were prehistoric. Others were not.

