Elephant's sixth 'toe' discovered

www.bbc.co.uk...

This CT scan reveals the sixth "toe" - here seen in dark green towards the back on the elephant's foot

A mysterious bony growth found in elephants' feet is actually a sixth "toe", scientists report.

For more than 300 years, the structure has puzzled researchers, but this study suggests that it helps to support elephants' colossal weight.

Fossils reveal that this "pre-digit" evolved about 40 million years ago, at a point when early elephants became larger and more land-based.

The research is published in the journal Science.

Lead author Professor John Hutchinson, from the UK's structure and motion laboratory at the Royal Veterinary College, said: "It's a cool mystery that goes back to 1706, when the first elephant was dissected by a Scottish surgeon."

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Anyone who has studied elephants' feet has wondered about it. They've thought: 'Huh, that's weird'”
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Professor John Hutchinson

Royal Veterinary College
Many people, he said, thought that the structure was a huge lump of cartilage, and over the years its purpose or lack of purpose has been debated.

"Anyone who has studied elephants' feet has wondered about it. They've thought: 'Huh, that's weird,' and then moved on," he added.

But Prof Hutchinson and colleagues used a combination of CT scans, histology, dissection and electron microscopy to solve the puzzle.

The researchers said the structure was made of bone, although bone with a highly irregular and unusual arrangement.

But closer examination also revealed that it showed a strong similarity with an unusual bone that is found in the front feet of pandas.

This bone - which is not quite an extra digit, but does the job of one - helps the panda to grip bamboo, and is called the panda's "thumb" or "sixth finger". Moles too have a bone masquerading as an extra digit, which helps them to dig.

And now, the team says that elephants can be added to the list of species for whom five fingers or toes are not quite enough.


The elephant's five regular toes give it a tip-toed stance Prof Hutchinson said: "It would have started out as a little nub in the tissue, which may have not even have been bone originally - it could have been cartilage.

"A lot of animals have these structures, cartilaginous lumps, and they sometimes turn to bone with these very different functions in some species."

For elephants, the structure serves a simple purpose: it helps the hefty animals to stand up.

Unlike pandas and moles, which only have the false digit in their front feet, elephants have the bone in all four of their feet.

And although their feet may look like tree trunks, inside the anatomy is more complex.

Their five conventional toes point forwards, giving elephants a tip-toed stance, but the extra "toe" points backwards into the heel pad, adding extra support and helping the heaviest land animal to hold up its bulk.

Evolution example

To find out when and why this strange bone appeared, the researchers examined elephant fossils.

Prof Hutchinson said: "The first elephants appear around 55 million years ago.

The sixth "toe" is an example of how a structure evolved to have a new function "We looked at early elephants and they had a different kind of foot, which seemed to be quite flat footed and didn't leave much room for this structure underneath.

"The structure seemed to evolved around 40 million years ago, and it seems to have evolved in concert with elephants getting bigger and more terrestrial and having upright feet, with a more tip-toed foot posture."

He added that this was a remarkable case of evolution in action.

He said: "It is a great example of how evolution tinkers and tweaks tissue to provide different functions - in this case to be co-opted to be used like a digit."

Science is one step closer in showing how evolution may work.

We didn't know a sixth toe existed on elephants but apparently we immediately knew that the toe 'evolved about 40 million years ago, at a point when early elephants became larger and more land-based'. Is it just me or are scientists becoming more and more like fantasy writers.

reply to post by Razimus


It's just more proof that we are extremely primitive scientifically and technologically speaking. And probably in just about every other sense you can apply it to as well.

And yeah, I don't trust anything about the "age" or "time duration" stuff really anymore.

They just base it on an old assumption. The truth is there is very little way to determine actual ages when we are talking about scales of tens of thousands of years (or anything older than that.)

It is highly probable that we humans don't know what the hell we are talking about in relation to time.

Have you thought that this extra toe could have been used as a defense measure millions of years ago?
But now that elephants don't have many natural predators it just retracted into their feet?

Imagine elephants had raptor-like feet where they have that back toe used for more balance and faster agility, haha!

reply to post by muzzleflash

It is highly probable that we humans don't know what the hell we are talking about in relation to time.

I agree. I don't think we currently have the ability to completely understand ANYTHING in relation to time.

reply to post by TheGrassHopper

Have you thought that this extra toe could have been used as a defense measure millions of years ago?
But now that elephants don't have many natural predators it just retracted into their feet?

I would think that there is a chance you are correct. This could be a perfect example of evolution doing away with something that is no longer required.

reply to post by Razimus

From the OP:

For more than 300 years, the structure has puzzled researchers, but this study suggests that it helps to support elephants' colossal weight.

Fossils reveal that this "pre-digit" evolved about 40 million years ago, at a point when early elephants became larger and more land-based.

Not sure why this explanation would qualify as fantasy.

I had no idea elephants had six toes, that's interesting.

Originally posted by isyeye

It is highly probable that we humans don't know what the hell we are talking about in relation to time.

I agree. I don't think we currently have the ability to completely understand ANYTHING in relation to time.

What are you folks basing these comments on? Do you know anything about dating of rocks?
geology.utah.gov...

The nuclear decay of radioactive isotopes is a process that behaves in a clock-like fashion and is thus a useful tool for determining the absolute age of rocks. Radioactive decay is the process by which a "parent" isotope changes into a "daughter" isotope. Rates of radioactive decay are constant and measured in terms of half-life, the time it takes half of a parent isotope to decay into a stable daughter isotope.

Some rock-forming minerals contain naturally occurring radioactive isotopes with very long half-lives unaffected by chemical or physical conditions that exist after the rock is formed. Half-lives of these isotopes and the parent-to-daughter ratio in a given rock sample can be measured, then a relatively simple calculation yields the absolute (radiometric) date at which the parent began to decay, i.e., the age of the rock.

As far as I know that can give something like +/- 10% so if they say 40 million years ago, that means something like 36-44 million years ago due to the 10% uncertainty, is that 10% uncertainty what you're talking about?

That uncertainty doesn't seem to justify your comments, so perhaps you can better explain what you know about this that the scientists have overlooked, or expose your own ignorance about the topic, whichever the case might be.

Originally posted by Razimus
We didn't know a sixth toe existed on elephants but apparently we immediately knew that the toe 'evolved about 40 million years ago, at a point when early elephants became larger and more land-based'. Is it just me or are scientists becoming more and more like fantasy writers.

This is simply called: "fling the theories until something sticks"
And THIS boys and girls are the same people who tell us aliens, Loch Ness and BigFoot don't exist because, they can't.

It's time we start thinking on our own.