Why We Only Have Ten Toes (It's a Long Story)

Today, all mammals from humans to bats have five fingers or fewer. Yes, even whales, whose finger bones are hidden in their fins. Birds have four or fewer and amphibians get the best of both worlds, often having four digits on their “hands” and five on their “feet.” But no species of vertebrates have more than five digits, let alone eight!

Thanks to these paleoartists for allowing us to use their incredible work in this episode!

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Produced by Complexly for Digital Studios

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[eons]

Many of you have correctly pointed out that reptiles usually have five toes. Unless you're counting snakes, with no toes. So maybe it averages out? Regardless, sorry about that mix-up and thanks to those of you who sent us that correction!

[conormcmullen]

Pederpes looks exactly like Pederpes should look with a name like that. I love it.

[HistoryScienceTheater]

Pandas basically have six fingers and I guess got around the whole, "the DNA that codes for how many fingers you have would mess a bunch of other stuff up if it mutated, " by not really adding another finger. Its just a finger sized outcrop of bone, no joint involved. So they basically have 5 fingers and a hand stick.

[kelseyhaddix]

Genes affecting digit development absolutely control other parts of development. I have congenital thumb hypoplasia, and also scoliosis. My daughter likely has the same gene mutation, she also has thumb hypoplasia, scoliosis, as well as radial dysplasia. She also had to be screened for heart and kidney deformities since they are common seen alongside these conditions

[MortyMortyMorty]

Imagine if we had 8 fingers each hand then we would calculate everything in hexadecimal 😄

[lauravansanten]

I really wonder: how is it possible that footprints fossilized eras ago, that have been exposed to the elements for who knows how long, are still preserved? I'd love an episode dedicated to trace fossils!

[Tfaonc]

Never have I ever thought to myself "what I really need here is an extra three fingers"

A third arm and hand? Absolutely! But I struggle to see a scenario where fingers beyond five give an evolutionary advantage, but they are extra complexity which is a disadvantage.

[AskMia]

3:23, is it just me, or do the three fingers together here look like a proto-thumb with four other fingers???? Did those three fuse into one??? If so, that is AWESOME! If not, it could still show that an angled set of fingers plus four straight ish fingers was somehow ideal for these tetrapods, and that is FASCINATING!!!

[BioniclesaurKingt]

0:58 "…but no species of vertebrates have _more_ than five digits."
Hemingway cats: "Please allow me to introduce myself…"

[lilren]

Someone mentioned pandas, and I would love an episode on how one of the most fearsome carnivores on the planet eventually sprung a lineage that is strictly herbivorous.

[KellyClowers]

Well, ichthyosaurs went kinda crazy with hand/finger bones. Granted those were embedded in a flipper, not fingers

[Aptonoth]

Wow I haven't been this early since the devonian period.

[helmutzollner]

Very interesting. About regaining more digits. There is sixfingered dwarfism. That leads to diminutitive growth and other health issues. So the hypothesis of the gene being used for more than one purpose rings true.

[leahime]

I don’t know if any will actually read this, but THANK YOU for respecting the audience’s intelligence in this video. Still concise and informative without being boring. Perfect middle ground.

[barbiquearea]

I've heard somewhere that the reason certain species of fish from the Devonian such as Tiktaalik evolved limbs that allowed them to go on land was so they could escape from perusing predators. But overtime these fish and their descendants evolved to become more terrestrial. This was because insects were already abundant all over the land, so evolving to become land-bound opened up a new ecological niche for these prehistoric fish, as now they can hunt for insects that were already on land.

[like-a-limestone_cowboy]

Wow! This video came at a perfect time- we’ve been discussing this topic in my evolution course just this week

[Rationalific]

Ironically, while it is supposed that whales won't gain legs again, we can point to them as an example of tetrapods gaining fins again.

[JustSomeKittenwithaGun]

That fish is the reason I have to pay bills.

[MichaelJBurnsII]

My nephew is polydactyl. He has 6 fingers on each hand and 6 toes on each foot. The toes are well formed and fully functional. The extra pinky finger on each hand is more just floating there and should probably be removed surgically.

[stormcat]

Another amazing Eons video. It’s incredible how you guys keep finding new interesting topics and then make both a well researched and engaging piece of content