
How Birds Evolved From Dinosaurs (2015) - ricardomcgowan
https://www.quantamagazine.org/how-birds-evolved-from-dinosaurs-20150602
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emmelaich
Just found this ...

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

> _notable for having chicks that have claws on two of their wing digits._

> _In 2015, genetic research[5] indicated that the hoatzin is the last
> surviving member of a bird line that branched off in its own direction 64
> million years ago, shortly after the extinction event that killed the non-
> avian dinosaurs.[6]_

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Scarblac
Given how much that looks like a bird, that strongly suggests we would also
recognize avian dinosaurs as birds, right?

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TomMarius
It hasn't remained the same for all that time.

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hansbo
For any feature this bird and other birds have in common to have come later,
they would have to have evolved twice. This could be the case for some
features, but is highly unlikely to be responsible for large part of the
similarities.

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titzer
The article is actually really interesting and has a lot more up-to-date
information than the title would suggest. For example, one new idea I gleaned
from this is that the evolution towards smaller body size happened long before
the extinction event 65 million years ago. Miniaturization stretches back at
least 200 million years. Other neat fact: early birds looked very much like
infantile or even embryonic raptors, suggesting that instead of evolving a
whole new set of traits, small modifications to embryonic development were
more likely. It seems this idea is also picking up in other areas of studying
evolution as well.

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hyperpallium
> early birds looked very much like infantile or even embryonic raptors

Sounds like neoteny, the retention of juvenile characteristics in adulthood.
See: domesticated foxes, dogs (esp toy breeds), people. Seems like a
particularly easy evolutionary path, perhaps take a step back, then forward.

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jdmichal
> New research suggests that bird ancestors shrank fast, indicating that the
> diminutive size was an important and advantageous trait, quite possibly an
> essential component in bird evolution.

This is making the common mistake regarding evolution. Evolution doesn't
select _for_ advantageous things, but _against_ disadvantageous things. It's
not survival of the fittest, but death of the inadequate.

It seems nitpicky, but it's very important for diversity. If getting larger or
smaller doesn't drastically hinder your survivability, then one ends up with a
large range of sizes.

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woodandsteel
Do evolutionary biologists generally agree with what you are saying? Is it
what I would be taught if I took a course in evolutionary biology?

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coldcode
Birds did not evolve from dinosaurs, they are dinosaurs.

Just read "Some Assembly Required: Decoding Four Billion Years of Life, from
Ancient Fossils to DNA" by Neil Shubin. The pathway how a current species
became what it is is quite surprising. Most features you see today came about
as copies of other features that were repurposed over time, like feathers did
not evolve to support flight, but for other reasons, and then lead to flight
later. This idea of repurposing started with a Darwin comment in his last
update to The Origin Of Species.

~~~
throwaway894345
I hear this a lot, but I don't understand in what capacity it is true. Why can
we say "Birds did not evolve from dinosaurs they are dinosaurs" but not
"Humans did not evolve from fish they are fish"?

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crazydoggers
Birds are part of what’s called the Dinosauria clade. Clades are monophyletic
meaning they encompass all the descendants of a common ancestor and all share
common traits.

Humans and fish on the other hand can’t be grouped into a clade. That’s
because it you trace back the common ancestor you’ll find other monophyletic
groups descending from those ancestors.

Think of a clade as the end of a branch and all its leaves... whereas if you
go far enough down you’ll find other branches that shoot off in other
directions far off, even though they’re in the same main trunk.

[https://en.m.wikipedia.org/wiki/Clade](https://en.m.wikipedia.org/wiki/Clade)

~~~
throwaway894345
This seems like a rephrasing of the claim "birds are dinosaurs". "Birds are
dinosaurs because birds are dinosaurs". Maybe the answer is "it's arbitrary;
scientists decided that birds belong in the group 'dinosaurs' even though
'dinosaurs' and 'birds' are clearly distinct groups to everyone else"?

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phonypc
Well, they're distinct groups to scientists too. Nobody is saying dinosaur and
bird are interchangeable terms. All birds are dinosaurs, not all dinosaurs
were birds.

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throwaway894345
No one is saying that someone is saying that the terms are interchangeable :).
The issue is that it’s not clear why “birds are dinosaurs” is correct but
“birds evolved from dinosaurs” is not.

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phonypc
I don't think "birds evolved from dinosaurs" is _incorrect_ per se, but it
evokes a common misconception of what dinosaurs are, so you get people
responding "birds are dinosaurs."

Consider by analogy "humans evolved from primates." Well ya, but humans also
_are_ primates.

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throwaway894345
I don’t think it’s a misconception at all, but rather science has its own
definition and lay people have another. The definitions are useful to their
respective camps. People who correct laypeople for using their definition are
boring pedants.

~~~
phonypc
I don't think that works. The lay persons definition is necessarily derived
from the scientific one. "Dinosaur" wouldn't exist as a word or concept
without scientific study.

Sorry to keep bringing up the same analogy, but do you also think it would be
pedantic to correct "humans evolved from primates" to "humans are primates"?

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throwaway894345
The analogy doesn't apply because "primates" doesn't have a colloquial
definition that excludes humans. "fish" or "reptiles" would be better
examples. "Humans didn't evolve from reptiles; they _are_ reptiles". I don't
find it pertinent that the colloquial definition wouldn't exist without
scientific study.

~~~
phonypc
Fish and reptile aren't comparable terms to dinosaur. They started as
colloquial terms and (as colloquially used) refer to groups based on traits,
not phylogeny. Humans actually _are not_ evolved from the phylogenetic group
closest in content to "reptiles."

I guess you could argue the colloquial definition of dinosaur is similarly
trait based, but even then... an ostrich is practically a small toothless T.
rex.

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emmelaich
"Paedomorphosis" doesn't sound _that different_ to the "Ontogeny recapitulates
phylogeny" observation.

Adds an interesting perspective on the controversy.

Link:
[https://en.wikipedia.org/wiki/Recapitulation_theory](https://en.wikipedia.org/wiki/Recapitulation_theory)

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mrfusion
Is there a picture anywhere of the chick embryos with the dinosaur like face
they mention?

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Jtsummers
[https://www.smithsonianmag.com/smart-news/chicken-embryos-
ge...](https://www.smithsonianmag.com/smart-news/chicken-embryos-get-dino-
snouts-thanks-biological-tinkering-180955250/)

That one has an image.

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sopooneo
Does this mean that distinct, non-flying species of dinosaur independently
evolved to be able to fly? Or does it mean that one species of dinosaur
evolved to have the ability to fly, and then further branched into all know
species of birds?

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loosescrews
According the the Wikipedia page on animal flight, dinosaurs and birds are
believed to have evolved flight independently.

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

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tsimionescu
Actually, according to that article _pterosaurs_ , that are explicitly _not_
dinosaurs, evolved flight separately from the dinosaurs/birds (with two other
separate times flight evolved mentioned, in insects and in bats).

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ajuc
Another time it evolved independently was in homo sapiens.

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thaumasiotes
> “Archaeopteryx seemed to emerge fully fledged with the characteristics of
> modern birds,” said Michael Benton

Pun intended?

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andrewflnr
It's almost not even a pun, just a literal statement. "Fledge" just means "to
become feathered".
[https://www.etymonline.com/word/fledge](https://www.etymonline.com/word/fledge)

~~~
ianmcgowan
Insert Simpson's <"That's the joke"> meme here...

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chewxy
This sentence strikes me as interesting:

> (For ethical reasons, they did not allow the chickens to hatch.)

What exactly is the ethical reason? Do they suspect that the dino-faced
chickens will not have a good quality of life? How do they know that? Also,
who doesn't want to see a dinosaur-faced chicken?

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DC-3
It's not a dino-faced chicken. It's a deformed-chicken-face chicken. You're
not going to get something cohesive by flipping a couple genes, you're going
to get something malformed.

Edit: a bit of googling suggests that, at least according to the scientist
leading the project, I am wrong here:

For now Bhullar has no plans, or ethical approval, to hatch the snouted
chickens. But he believes they would have been able to survive "just fine".

"These weren't drastic modifications," says Bhullar. "They are far less weird
than many breeds of chicken developed by chicken hobbyists and breeders."

"The rest of the animal looked OK, but one needs to think about this carefully
from an ethical point of view."

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mrfusion
I never understood why bipedal locomotion would evolve in dinosaurs.
Especially since the article says it happened well before any kind of flight
or even gliding.

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danieltillett
Bipedal locomotion is more efficient in that it takes less energy to cover a
certain distance on two legs than four.

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mrfusion
I never thought about that. I wonder why it hasn’t evolved more often then?
Basically limited to humans and birds. (I guess kangaroos too?)

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emmelaich
Many animals are occasionally bipedal. Apes and monkeys and similar of course.

But also bears and no doubt many more.

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dboreham
Domestic cats will stand up on their hind legs to see further.

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mcv
Not of those are efficient runners in that position, though. It's a careful
balancing act.

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nn3
"Former senior writer"

One idly wonders what must be going on at Quanta that she ended up with such a
title.

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romanhn
The article is from 2015. From the profile, it sounds like she no longer works
there and the profile was updated to reflect that.

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traes
I think the original title, " _How_ Dinosaurs Shrank and Became Birds," would
do this article more justice. The title makes it seem like the article is just
discussing a well known fact, but it actually goes quite in-depth.

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dang
I've re-howed it.

