"...the claim that birds have genes for teeth likely centers around a 2006 study of a mutation in chickens called talpid2, which is a lethal recessive mutation that causes several developmental defects in chick embryos (Harris, et al., 2006, pp. 371-377).
This mutation has been studied for over 60 years, and the 2006
study suggested that embryos with this mutation appeared to be developing a tooth-like structure before death (Harris, et al.).
Evolutionary interpretations of these findings suggest that this mutation must indicate that there is some vestigial genetic programming for tooth development leftover in the genomes of chickens (“Mutant Chickens Grow Teeth,” 2006).
But important points need to be made regarding those interpretations.
First, the talpid2 mutation is known to impact the developmental gene called sonic hedgehog (shh), which plays critical roles in body plan patterning and development. Thus, it is no surprise that this mutation may cause drastic changes in body structure.
Second, this mutation is lethal; so, clearly, it does not offer any benefit for the organism.
Third, at the time of the 2006 study, the actual gene involved in this mutation was unknown. However, that gene has now been identified as C2CD3 (Chang, et al., 2014, pp. 3003-3012). This study noted that the actual function of the protein produced from this gene is not known, but they provided evidence that a deletion within this gene caused the talpid2 phenotype.
Interestingly, this gene is somehow involved in production of cilia and the protein product is detectable in cells. Thus, far from being a “gene for teeth,” this gene appears to be important in embryonic development and somehow plays a role in cilia formation.
Certainly, more details will be forthcoming as research continues, but this example does not support the idea that “birds have genes for teeth.” That said, it should be noted that there are examples of birds with teeth (e.g., Archaeopteryx; also, there is an egg tooth that is used to break out of eggs). So, we would not be surprised to find other birds with the genetic information to produce such structures, but the existence of those abilities in no way implies that birds evolved from animals with teeth. Further, it is also possible that there may be birds that have lost the ability to produce teeth through genetic mutation, but again, the talpid2 mutation does not appear to be such a case." AP
This mutation has been studied for over 60 years, and the 2006
Evolutionary interpretations of these findings suggest that this mutation must indicate that there is some vestigial genetic programming for tooth development leftover in the genomes of chickens (“Mutant Chickens Grow Teeth,” 2006).
But important points need to be made regarding those interpretations.
First, the talpid2 mutation is known to impact the developmental gene called sonic hedgehog (shh), which plays critical roles in body plan patterning and development. Thus, it is no surprise that this mutation may cause drastic changes in body structure.
Second, this mutation is lethal; so, clearly, it does not offer any benefit for the organism.
Third, at the time of the 2006 study, the actual gene involved in this mutation was unknown. However, that gene has now been identified as C2CD3 (Chang, et al., 2014, pp. 3003-3012). This study noted that the actual function of the protein produced from this gene is not known, but they provided evidence that a deletion within this gene caused the talpid2 phenotype.
Interestingly, this gene is somehow involved in production of cilia and the protein product is detectable in cells. Thus, far from being a “gene for teeth,” this gene appears to be important in embryonic development and somehow plays a role in cilia formation.
Certainly, more details will be forthcoming as research continues, but this example does not support the idea that “birds have genes for teeth.” That said, it should be noted that there are examples of birds with teeth (e.g., Archaeopteryx; also, there is an egg tooth that is used to break out of eggs). So, we would not be surprised to find other birds with the genetic information to produce such structures, but the existence of those abilities in no way implies that birds evolved from animals with teeth. Further, it is also possible that there may be birds that have lost the ability to produce teeth through genetic mutation, but again, the talpid2 mutation does not appear to be such a case." AP
