I read with fascination this week that the genes in charge of growing appendages (arms, legs, fingers, toes, wings, tentacles…) are now thought to predate the point at which our lineage diverged from that of the octopus. This is despite the fact that octopi, insects, and vertebrates each evolved their very different limbs independently. The same gene determines the number of fingers we have, and the number of suckers an octopus has, and Martin Cohn and his colleagues have now shown that this genetic program dates back at least 500 million years.*
This article inspired me to take a close look at fingers and toes. It turned out to be quite hard to find good photos in my archives: most of the time animals stand in long grass, or in muddy water, hiding their feet, but here goes. (None of these posts pretends to be a full scientific survey: the limiting factor is what I have photos of.)
I think I’ll start with us mammals. Unlike the Pobble, they all have toes, but the number of toes varies from six to one….
Mountain gorillas, not surprisingly, have the the same number of fingers and toes as us:
Giant otters also have five toes on each foot, but they are webbed:
Elephants have five toes, but they walk on tiptoe, so the toe nails are the only way to count. Like pandas, they have a sixth “toe”. It is inside their foot, and it may help distribute their weight better.
Lions, and other cats, have five front toes and four back ones. Here are the five:
and here are the four:
Hippos have four webbed toes on each foot, supporting their enormous weight (you can’t see the fourth toe in the photo):
Warthogs, like all pigs, have four toes on each foot but they walk only on the middle two, holding the others clear of the ground, for all the world like a ballerina en pointe. (At speed, these smaller claws may touch the ground. ) So really they have two proper toes.
All tapirs, including this South American one in the Pantanal, have four front toes and three back ones. They are the only hoofed animal like this.
Rhinoceri have three toes on each foot:
Giraffe (and cattle and deer) have two toes, and the dew claws are insignificant:
Zebras, and all equines, have all five digits merged into one toe (aka hoof) per foot:
It’s also worth remembering that our bodies are left-right symmetrical, so our big toes are on the inside of each foot. Our development thus has not just to get the count right, but arrange each foot appropriately for which side of the body it emerges from. How clever is that?
Next time, we’ll look at birds.
‘The Pobble Who Has No Toes’
The Pobble who has no toes Had once as many as we; When they said "Some day you may lose them all;" He replied "Fish, fiddle-de-dee!" And his Aunt Jobiska made him drink Lavender water tinged with pink, For she said "The World in general knows There's nothing so good for a Pobble's toes!" The Pobble who has no toes Swam across the Bristol Channel; But before he set out he wrapped his nose In a piece of scarlet flannel. For his Aunt Jobiska said "No harm Can come to his toes if his nose is warm; And it's perfectly known that a Pobble's toes Are safe, -- provided he minds his nose!" The Pobble swam fast and well, And when boats or ships came near him, He tinkledy-blinkledy-winkled a bell, So that all the world could hear him. And all the Sailors and Admirals cried, When they saw him nearing the further side - "He has gone to fish for his Aunt Jobiska's Runcible Cat with crimson whiskers!" But before he touched the shore, The shore of the Bristol Channel, A sea-green porpoise carried away His wrapper of scarlet flannel. And when he came to observe his feet, Formerly garnished with toes so neat, His face at once became forlorn, On perceiving that all his toes were gone! And nobody ever knew, From that dark day to the present, Whoso had taken the Pobble's toes, In a manner so far from pleasant. Whether the shrimps, or crawfish grey, Or crafty Mermaids stole them away - Nobody knew: and nobody knows How the Pobble was robbed of his twice five toes! The Pobble who has no toes Was placed in a friendly Bark, And they rowed him back, and carried him up To his Aunt Jobiska's Park. And she made him a feast at his earnest wish Of eggs and buttercups fried with fish, - And she said "It's a fact the whole world knows, That Pobbles are happier without their toes!" Edward Lear
*Here is a short summary of Martin Cohn’s findings: