left-handed animals

There is some sort of crab with one claw that dwarfs the other one by about five times. I think the small claw is the preferred one (for dexterity, obviously not for crushing things), but I can’t remember. I saw this on a nature show or something; a scientist was trying to figure out how they developed their clawed-ness so they could get some clue about human handed-ness development.

The classic column being referred to is:
http://www.straightdope.com/classics/a4_085.html
Always good to post that along with your message so others can read the article you’re referring to. Thanks!
Jill

Fiddler crab, I believe.


John W. Kennedy
“Compact is becoming contract; man only earns and pays.”
– Charles Williams

One should avoid trying to turn a left-handed cat into a rightie…they never learn to write or type well with their right paws! :slight_smile:

I just pointed a co-worker to this site, and she noticed this topic. Polycarp, please note the exception to your rule.

She grows catnip (in a hanging basket, so it survives) and keeps the harvest in a jar. One of her cats is right-pawed when it rakes out the first couple of hits, but as soon as the drug kicks in, the cat uses the left paw, and stays left-pawed until it’s straight again.

Now there’s a good subject for handedness research! :slight_smile:

Bob the Random Expert
“If we don’t have the answer, we’ll make one up.”

The paws that are refreshed.

Ray

Yes, the male fiddler crab has one claw much larger than the other. During courtship, the male waves the big claw around in order to attract a mate. The larger and more prominent the claw, the better chance to get the girl. Don’t know if there is a consistent bias for size based on left or right, however.

I noted that Cecil referred to several mammals that exhibited a “handedness” trait. The distribution was listed as 50/50, (i.e half right-handed, half left-handed). My question is why aren’t humans 50/50 (right vs. left handed). I seem to remember something from Roman history about left-handers being persecuted/executed. Also, I think left in Latin is “sinister”. I’m surprised that Cecil didn’t mention this, what gives?

Here ya go:
Hypertext Webster Gateway: “sinister”

From Webster’s Revised Unabridged Dictionary (1913) (web1913)

Sinister \Sin"ister\ (s[i^]n"[i^]st[~e]r; 277), a.

Note: [Accented on the middle syllable by the older poets, as Shakespeare, Milton, Dryden.] [L. sinister: cf. F. sinistre.] 1. On the left hand, or the side
of the left hand; left; – opposed to {dexter}, or {right}. ``Here on his sinister cheek.’’ --Shak.

I would give my right arm to be left handed…

OK, Cecil never said that animals were 50/50 on the handedness/pawness issue. He stated that certain studies had shown that certain animals were more likely to be right or left pawed, and that chimps were about equally distributed on the left/right handedness issue.

One more comment about it, from a horseman from way back: Most of the horses I’ve worked with over the last 30 years have been left-hooved, except Thoroughbreds, who have tended to be right hooved. I shouldn’t say hooved, here. Most of the horses I’ve worked with have been left dominant, except the TBs who have been right dominant. In horses, you can see by muscle development, rather than which hoof they use to write with.

And my current crop of cats are two thirds left dominant, with one who has to relearn the entire world everyday, and switches from left to right once or twice a week, though generally right dom.

Here’s what the column stated:
“Paw/claw/whatever preference is actually pretty common in the animal world, having turned up in most species
tested, including parrots (mostly lefties) as well as rats, monkeys, and chimpanzees (50-50 right versus left).”
Therefore, from the limited information presented, MAMMALS tested exhibited a 50/50 distribution of right or left handedness.

My restated question is: Who killed off all the left handed people?

A) Riding horses have at least one human-induced asymmetry.

B) Human brains are far more specialized right-left than most critters’.


John W. Kennedy
“Compact is becoming contract; man only earns and pays.”
– Charles Williams

John, the riding horses you refer to may have been influenced by humans, but I can tell you that foals are naturally left or right dominant from the start. That’s one of the challenges in training them, because at first ALL horses want to stick to their dominant sides.

Also, to whoever keeps saying that right and left dominance is 50/50 split: that line still tells me that chimpanzees are split 50/50, not all the mammals. Give me some more proof.

As for left and right humans, I think it may be Tim White’s theory, but I know I read somewhere that the stronger maternal heartbeat on the left side led to prehistoric women carrying babies on the left hip, which gave an advantage to right dominant women in passing on their genes. Holding the babies on the side with the stronger heartbeat helped calm the babies, since they’d spent the past nine months hearing that same ‘glumph-glumph’ sound. Not my theory, but I like it. It explains something without having to call up flying monkeys…

So, what else happened to the lefties? You know that lefties tend to die younger from accidents than righties, and that for centuries lefties were shunned. Probably because they were said to be witches or the equivalent. Well, that may just be that they were so much smarter than the average that they frightened everyone, at least that’s a theory that explains Cecil…

[[I think it may be Tim White’s theory, but I know I read somewhere that the stronger maternal heartbeat on the left side led to prehistoric women carrying babies on the left hip, which gave an advantage to right dominant women in passing on their genes.]]

I don’t get this. You use your left arm to carry a baby on the left hip.

Your left arm is tied up holding the baby while the right arm is free to pick berries, pull roots, stir cook pots, put more wood on the fire, etc.

That whole concept might be backwards, though. Just how much difference does it make to the baby to be on the left side or the right side? Seems more likely to me that carrying the baby on the left hip became customary because most women were right-handed, not that most women became right-handed because they carried the baby on the left hip.


I have as much authority as the Pope; I just don’t have as many people who believe it! - George Carlin

Humans are unusual compared to other animals in that they have fairly complex speech.

Wernicke’s area is one area identified with the same (causes aphasia if damaged)
It is on the left side of the brain.

"Most people (about 80 per cent) are right-handed <4> and in the vast majority of right-handed people, the ability to organise speech and the ability to speak are predominantly localised in the left side of the brain. But the right side can understand written and spoken language to some extent at least. {14}

“Appreciating spatial perceptions depends more on the right hemisphere, although there is a left hemisphere contribution. This is especially true when handling objects” {14} and concerning abstract geometric shapes and music."

In other words, if a certain area of the human brain became associated with speech, and this was on the left side, there would be a selection pressure for left side dominance, which would result in right-handedness.

Some very interesting work in this area is contained in a lengthy article in the current *Annals of Mammalian Etiology,</> Vol. C, No. 2525. The eminent Dr. Haans N. Bothaphete of Cape Town University writes
extensively of his studies in the bush (Africa and Australia). Among his conclusions:

Kangaroos, when “boxing,” invariably lead with their left paw
before using their right leg to administer the coup de
pouch.

Flamingoes almost universally sleep standing on their right leg with their beaks tucked beneath their left wing. Those few which stand right and tuck left, he reports, are swiftly ostracized from the flock.

Perhaps most startling, Dr. Bothaphete has discovered ambidexterity in conjunction with surprising language sophistication among the lowland gorillas of Rwanda. He observed these shy creatures using both hands to sign to each other with equal ease. After many weeks of close observation, Dr. Bothaphete was able to learn the rudiments of their language, deciphering in one amazing encounter a female, signing to the biggest of the male silverbacks:

“Banana in paw that is, or happy you to see me are?”

You know, you had me completely fooled until the “banana” line.

:slight_smile: