Saturday, March 22, 2008

Question: Can anyone give me an evolutionary explanation for why babies have an insatiable need to stick everything they see--much of it dirty--into their mouths?

11 comments:

TGGP said...

They're dumb. Babies brains kept expanding while the mother's waist couldn't keep up, so they are less independent when they are born than other animals (I believe deer can walk from the start, for instance). A lot of learning must take place during those early years, including the notion that there are some things not to be stuck in mouths.

MensaRefugee said...

Guess they are meant to be supervised closely for the first couple of years...

Jeff Burton said...

I don't believe in evolution and I could give you half a dozen. It's a simple act of the imagination.

RobertHume said...

Young children don't like vegetables and that might be because many green plants are poisonous. (You have to be taught to eat your vegetables.) Whereas sweet and fat things are usually not.

Dirt or twigs or anything shiny is not usually poisonous; even excrement you can survive better than laurel or poison ivy. Kids who ate laurel didn't have kids.

Byrne said...

Perhaps taste develops faster than other senses, so it's actually the best way to get information. And if we're just talking taste, not smell, we're not going to encounter that many in a lifetime. So perhaps they taste things as often as adults glance, sniff, or listen -- but adults don't have the urge to taste because we've tasted it all.

Anonymous said...

Prolly something to do with learning what to eat and what not to eat. Something to do with being a primate as infant humans share this behavior with other primate infants. I know that orang and gibbon and lemur infants will try nibbling on different items in their environment while they're hanging on to mom and learning from her what's edible.

Theresa

Anonymous said...

One reason suggested is for their intestinal lymphatic system to get acquainted with different antigens from their environment. Thats one reason why babies in industrialised urbane environments suffer from allergies and autoimmune diseases in far greater frequency than babies in dirty, rural or poor environments.
Also babies whose immune systems have been exposed to small inocula of potential harmful bacteria develop stronger defenses later, should those (common) bacteria atack their bodies in times of vulnerability. Nowadays some pediatricians actually advise parents today not to be too strict on their children about this behaviour for these reasons.

Anonymous said...

It's multi-factorial.
First off, when they are very young they have a rooting reflex which is designed to attach baby to breast.

The behavior you see later on where children "test" objects with their mouth is because the mouth has the densest clustering of tactile nerve endings of any skin surface on the body and as such the best two-point discrimination* available to the child's nascent sensory system. Babies are learning machines-- they put objects in their mouths because it is the best way to become familiar with the contour of the object. The evolutionary reasons for why human babies are particularly good learning machines (and why they are more "soft-wired" than most other animals.) I'll leave up to you to determine...



*(Two point discrimination is a measure of the closest two discrete sensations can be without being detected as the same source.)

Anonymous said...

It's multi-factorial.
First off, when they are very young they have a rooting reflex which is designed to attach baby to breast.

The behavior you see later on where children "test" objects with their mouth is because the mouth has the densest clustering of tactile nerve endings of any skin surface on the body and as such the best two-point discrimination* available to the child's nascent sensory system. Babies are learning machines-- they put objects in their mouths because it is the best way to become familiar with the contour of the object. The evolutionary reasons for why human babies are particularly good learning machines (and why they are more "soft-wired" than most other animals.) I'll leave up to you to determine...



*(Two point discrimination is a measure of the closest two discrete sensations can be without being detected as the same source.)

Nathaniel said...

The previous comment seems to be what most people accept as the reason why babies put everything in their mouths. They have a predisposition to suck (because of breasts) and their most sensitive sense of touch is on their tongue. They explore their world by putting things in their mouth.

The vegi idea is also a good one. That's also why pregnant women get morning sickness. As we grow we're able to process the toxins from plants, but as babies we are very susceptible to the damage they can cause. It would be interesting to find out if babies are more likely to put... let's say car keys instead of broccoli in their mouths.

Right Wing Hippie said...

The green plants=poisonous hypothesis doesn't convince me, because my kids ate EVERYTHING I put in front of them until about 18 months or so. I was so proud of how many veggies they would eat...that all changed as they got older, though.

And, in contradiction to the theory that it is because the mouth gives them so much sensory input, my kids seemed not to actually taste anything as infants and young toddlers. I mean, they would eat spicy things, strong-flavored foods -- all of them loved to suck on a nice garlicky pickle or a lemon wedge, and they would eat Thai food as infants but sometime around 18 months the taste buds seemed to kick in and they suddenly only wanted bland "kid foods" like noodles and applesauce.

Could it possibly have be a form of selection that favors more vigilant parents? For example, a mother who did not keep an eye on what her infants were putting in their mouths would presumably have fewer offspring survive to adulthood as a result of choking or poisoning?