Question about teeth evolution.

[Bango Skank]

Hi,

I am 30 years old, yet i still have one milk tooth left in lower jaw. I once had a brief conversation about it with a dentist and it surprised me to learn that it is pretty common (at least in my country). For some people there isn't any tooth development at all in that place and some have similar phenoma in opposite lower jaw tooth. Tooth in question is a tooth number 5 in lower jaw (in dentist language). I hope you get what i mean.

So my question is, what is causing this to happen? Is it a result of harmful mutation?

 

[Master_Ghost_Knight]

Some people have wisdom teeth that grow inwards which can infect, causes the person a lot of pain and they need to be surgically removed.
I on the other hand don't need them to be removed because they fit into my jaw. I mean I have one in my lower left jaw completely exposed, I have other 2 (one in my right lower and another in my left upper) which are there on the jaw but will never bud, on my right upper jaw there is nothing there.
We don't actually use them so there is no advantage in having them, nor do we wear of our teeth as a shark does so we don't actually need that much for a new pair (although it would have been useful at an old age).
However although there is a genetic component to the development to many tooth "anomalies" (like the wisdom teeth), it doesn't necessarily mean that all anomalies are genetic, for instance a disease contracted in childhood could affect the development of teeth in their critical stage.

Is it a result of harmful mutation?

Have you been harmed by it?

 

[Bango Skank]

Some people have wisdom teeth that grow inwards which can infect, causes the person a lot of pain and they need to be surgically removed.
I on the other hand don't need them to be removed because they fit into my jaw. I mean I have one in my lower left jaw completely exposed, I have other 2 (one in my right lower and another in my left upper) which are there on the jaw but will never bud, on my right upper jaw there is nothing there.
We don't actually use them so there is no advantage in having them, nor do we wear of our teeth as a shark does so we don't actually need that much for a new pair (although it would have been useful at an old age).
However although there is a genetic component to the development to many tooth "anomalies" (like the wisdom teeth), it doesn't necessarily mean that all anomalies are genetic, for instance a disease contracted in childhood could affect the development of teeth in their critical stage.

Sorry, i should have researched the proper name before making a post. What i meant was a mandibular second premolar (so not milk tooth after all).

http://en.wikipedia.org/wiki/Mandibular_second_premolar

"It is a very common condition in orthodontics for a patient to have one or both mandibular second premolars congenitally absent."

What i have so far gathered, the cause of them missing is unclear.

Is it a result of harmful mutation?

Have you been harmed by it?

Although i still have the tooth, it's not fully developed. It's a minor annoyance.

 

[Master_Ghost_Knight]

Although i still have the tooth, it's not fully developed. It's a minor annoyance.

Then it is probably not harmful.

 

[Bango Skank]

Well maybe this was a useless topic. I was just curious if there was a evolutionary explanation for this (like there is for wisdom teeth).

 

[Master_Ghost_Knight]

Well maybe this was a useless topic. I was just curious if there was a evolutionary explanation for this (like there is for wisdom teeth).

As you can realize not everyone has this, actually a very limited number of people has this. It can not be said to have an evolutionary reason.
Many royal monarch suffer from hemophilia, can't say that there is an evolutionary advantage to that.

 

[he_who_is_nobody]

To be honest, I have never heard of someone missing his or her second (fourth, depending on how you look at it) premolar. My assumption for why it would be missing in any population is the same for why some people are born without wisdom teeth (third molar). A mutation has come along that stops the jaw from creating the third molar. As Master_Ghost_Knight pointed out, we no longer need our third molars; they were once useful when we did not have oral hygiene. Your premolars and molars are used to crush up your food; they would wear out over time based off simple use and no oral hygiene. That means the more teeth you had in your jaw (coupled with different eruption times) would allowed individuals to live longer in life. Furthermore, one has to remember how much easier food is to eat presently compared to even 200 years ago, let alone several thousand or million years ago.

Long story short, what I think happened with you is in your population a similar mutation that stops the third molar from growing happened to your second premolar. Since there is no longer a disadvantage to having less teeth, because of oral hygiene, that trait has been passed along in your population. Since there is no selective pressure for it, it may never be fixed in the human population, but it can stick around for quite a long time because there is no pressure to remove it from our population as well.

Loss of teeth has happened in our ancestors before. As I said before, I would call that tooth the fourth premolar and that is because our ancestors had four premolars (on each side). Over time, they lost the first premolar and some modern primates have this tooth pattern, and our ancestors lost the second premolar, leading to us having only two premolars today.