No, this isn’t about Neil Shubin’s wonderful book about fossils, fishes, and evolutionary remnants, but a an article by Dr. Michael Mosley on, oddly, the BBC News “health” page. You must see it, if only to watch the 30-second time-lapse video (made from high-quality scans) of the development of the embryonic human face up to ten weeks. As Mosley explains (and the video shows), our fishy ancestry explains that curious groove between our nose and upper lip, the philtrum. Have you ever wondered why it’s there? It doesn’t have any obvious adaptive function. It’s an evolutionary remnant.
The video (which I’m unable to embed) shows this clearly, but Mosley explains:
The early human embryo looks very similar to the embryo of any other mammal, bird or amphibian – all of which have evolved from fish.
Your eyes start out on the sides of your head, but then move to the middle.
The top lip along with the jaw and palate started life as gill-like structures on your neck. Your nostrils and the middle part of your lip come down from the top of your head.
There is no trace of a scar; the plates of tissue and muscle fuse seamlessly. But there is, however, a little remnant of all this activity in the middle of your top lip – your philtrum.
This whole process, the bits coming together of the various elements to produce a recognisable human face, requires great precision.
To fuse correctly the three sections must grow and meet at precisely the right time in the womb.
If the timing is out, by as little as an hour, the baby may grow up with a cleft lip or cleft lip and palate, which can be extremely disfiguring. Around the world one in 700 babies are born with clefts.
The incipient philtrum (screenshot from the video)
Mosley also explains two other odd developmental features explained only as remnants of a distant ancestry: the descent of our gonads (sound like the title of a Darwin book) from the body cavity, and hiccups, a series of spasms that is uncomfortable for us but was adaptive in our amphibian ancestors.
56 thoughts on “Our inner fishes”
It would be good if someone would use this video, and at the end play it in reverse with the various parts labelled, e.g. “Top lip/Gill”
I’d do it myself, but I don’t know the biology 🙂
Would be good to watch one of these for fish too!
That’s what I was thinking.
The argument seems a bit sketchy to me. It sounds an awful lot like discredited recapitulation theory to me. All it really shows is that the philtrum is an artifact of the ontogeny, not that it had anything to do with evolving from fish. You can say that about any common ancestor. Pick any characteristic, find the latest common ancestor of all species with that characteristic and voilà, the cause was having descended from that ancestor. You haven’t really said anything at all about the cause, though, have you?
Although you often hear this, recapitulation theory is not TOTALLY discredited. It is, in fact, true that many developmental stages mirror the development of our ancestors, like the hairy coat that we humans develop (and shed) at six months in utero. Too, as PZ wrote about lately, we develop three kidneys in a row, the first two (which disappear) being homologous to ancestral kidneys.
When people say that “recapitulation theory is discredited,” I think they mean only that every organism goes through development in a sequences of ancestral stages. That’s not strictly true–some of those stages don’t appear, and some develop straight. But there certainly is a large amount of recapitulation in development.
I dealt with children with midline cranial defects – cleft lip and palate and nasal encephaloceles – for many years. These lesions make sense only in the light of developmental biology, and the video shows the process very well. Whether or not fish are our most recent common ancestor to illustrate this process I’m not sure, but it certainly puts them in our ancestral line, even if only as …nth cousins.
That is nonsense. The “cause” of ANY anatomic feature (either during embryonic phase or adulthood) is inheriting it. That the strict haeckelian capitulation (that you have to go through a phase similar to all your evolutionary ancestors during the development) is not true, it is also not true that you “shed” all those similarities. A good example is human spine. It is clearly not meant to bear weight, evidenced by the booming business of orthpedic and neurosurgeons. The “reason” it is there is that we have interited it from our chordate ancestors.
I do see what Brian’s saying though.
As the article says, the philtrum is the result of “all that activity” in the upper lip area. Presumably, any kind of complicated sewing together of parts could produce an odd structure such as the philtrum. But an odd sewing together of parts itself is not evidence of a fishy origin. The evidence of a fishy origin comes from what we know about this particular sewing together, which is that it starts with gill arches and develops with certain parts of the face in places where they would be for a fish (e.g. eyes on the side of the head), and then changes to become a human face.
Contrast this with the gonads example. Fish gonads and human gonads both form in the body cavity. That’s an odd thing to be a coincidence. Perhaps there is an evolutionary answer.
But a complicated sewing together of parts of the face produces a philtrum? That’s not really odd. In fact, it’s kind of normal. It only gets interested when you look at why the parts of the face come together in such a complicated way to begin with.
This bit of the programme was interesting, but I must confess to being disappointed with the rest of the first episode (shown last night).
There was a lot of the “you are the most amazing creature ever on Planet Earth! Go you!” flattery that is presumably supposed to make non-sciency people want to watch it. As a non-scientist myself I found it patronising.
I also thought it sad that the human interest angle felt a bit like a freakshow; the conjoined twins were inevitable, but the couple with 16 children and counting was just gross and had no bearing on the subject of the show.
Most disappointing: the fusion of sperm and egg apparently comes to an end once the sperm binds with the zona pellucida. Nothing about genetic recombination was even mentioned.
Uh, forgot to say: this video is from a TV series called The Human Body which started last night on BBC2.
I haven’t watched it yet but I do fear that it being a BBC1 documentary means there will be a bit too much awe-fluff for my tastes, as there was with Brian Cox’s recent physics series. I tend to prefer this sort of stuff when BBC4 do it; their smaller budgets seem to force them to put more actual science in the shows because they can’t afford lots of computer graphics and shots of waterfalls and glaciers, or so it seems to my eyes. (And relatedly BBC4 has an Iceland series next week, which will provide them with yet another opportunity to show the geysers and glaciers which seem mandatory in every BBC documentary these days. I’m surprised they don’t have a permanent unit set up there.)
Dave, it’s a bit like that. Having watched some of Mosley’s excellent documentaries on BBC4 before, I was hoping for more of the same. “The Brain: A Secret History” last year was outstanding.
The Adam Rutherford programmes, The Gene Code, were very good I thought & did not talk down. It depends what the intended audience is really. Before 9pm I expect fluffier programming, after I expect not to have everything explained from first principles.
Adam Rutherford is a Nature editor – I wonder if he was involved with the Nowak article…?
Doesn’t recombination occur during production of sperm and eggs, not during fusion of the sperm and egg? What would you have liked to see them explain in more detail?
There’s recombination from crossing over (Meiosis I) and there’s recombination from syngamy (combining genes that rose in on different gametes).
I’d never heard the latter termed recombination before…
Sorry – IANAS (I Am Not A Scientist) but it was the latter that I meant.
Seeing this, it boggles the mind why people resist the reality of evolution.
“that curious groove between our nose and upper lip, the philtrum.
Have you ever wondered why it’s there?”
God put it there to give us a place to keep our moustaches?
Moustaches, yes, and it’s also a good collection spot for chocolate frosting or strawberry jam!
The article is on the BBC’s website because it’s a plug for a new bbc series.
Wow– face tectonics! Had to watch that video three times– took a minute to figure out that the first holey -things weren’t eyes, but nostriches…
(In the middle of Dr. Shubin’s book– it *is* excellent! Highly recommended if you haven’t read it yet:-))
Nostriches? Not nemus, nassowaries nor noas?
:-)) According to my friend’s three-year-old (English-speaking), it’s ‘nostrich’…
I rarely watch TV, but I happened to get home just in time to watch this with my supper last night.
I really enjoyed it and thought that all of the human interest angles worked really well (identical twins, conjoined twins, 16 children, cleft pallet surgery, African mother etc).
I would have liked a better narrated section on the animation that Jerry mentions.
Also, I totally agree with embertine’s point that there should have been plenty of discussion about what happens once the sperm enters the egg.
However, I think it is possible that the sense of wonder that the producers of such programs try to produce is good and important, and may actually be one small part of replacing certain functions provided by organised religion.
Anyway, I recommend that you try to watch it!
Felix, yes, the cleft palette surgery was very interesting, and the contrast in healthcare between the triplet lady and the African girl who had to walk to the clinic was stark and thought-provoking.
I thought it a bit odd that two divers mentioned that they thought they were mirror twins, but the programme didn’t go no at all to explain what that meant.
I’ve always had an urge to eat a fly when I hiccup. Now I know why!
Perhaps you’ll die.
All I get is “Not available in your area”; how are non-British viewers accessing this video?
I can see it. Maybe Racine is BLACKED OUT! Lol!
If it’s not, it should be…
Actually, I was in Kenosha when I got “Not available in your area.” Now that I’m in Racine, it’s working!
And it’s still not available in Kenosha.
Usually the BBC vids are restricted to UK viewers. Personally I don’t see the point: what little extra cost there would be for the extra bandwidth would probably be made up many times over with purchases of BBC programmes.
Does anyone else find that first photo erotic? Maybe TMI…
I can relate to that. 🙂
Too Much Information
Srsly, Felix. Don’t claim to relate to acronyms you don’t know. Like NAMBLA…
I wasn’t relating to the acronym!
If you found the second photo erotic we would be worried. In fact, if you do, keep it to yourself :p
Interesting, to say the least.
Well I never ~ Love Potion…
What – even gentiles?! I know it is a story but why would it waste its time only to make the child forget?! 🙁
Because it must not be TOO easy to be wise & good I suppose. I discovered this nonsense on the www:
Is the philtrum a spandrel ?
Indeed it is. Though I still don’t see why the fact of a seam in the face means we get a philtrum, is it impossible to make a flat seam?
I wonder if it isn’t really a spandrel…
The philtrum changes the shape of the upper lip & perhaps the whole triangular assembly of nose, philtrum & lips is sexually selected ~ shape, redness etc
Lips lushness is a good indicator of youth ~ hence collagen injections. It’s reasonable I think to regard the philtrum as having a ‘cuteness’ factor
I think it’s basically a spandrel, but that’s not to say that it couldn’t become the object of sexual selection later on… to the Japanese it’s there to form a nice Mt. Fuji upper lip like a geisha…
Fun fact! 🙂
The new Inside The Human Body show is really great. I watched that first episode yesterday and it was extremely well made and even humbling in parts.
I saw that someone put it on Youtube in 4 parts, though it’s probably illegal and will be removed, but I highly recommend watching it.