Scientific Findings on Tooth-Related Genes in Modern Birds
1. Shared inactivating mutations in tooth genes
Researchers analyzed genomes of nearly all orders of living birds and found that key genes normally required for making mineralized tooth tissues — such as dentin and enamel-related genes — carry inactivating mutations in every species examined. These mutations (e.g., frameshifts, stop codons) likely render the genes unable to produce functional proteins for tooth formation. This suggests that the genetic machinery for building teeth is still there in a degraded form, but no longer active. PubMed
Specifically, genes like ENAM, AMELX, AMBN, AMTN, DSPP, and MMP20, which are essential for enamel and dentin formation in other vertebrates, all show mutations in modern bird genomes. These shared changes indicate these genes were once present but have since been inactivated across the avian lineage. PubMed
Ichthyornis, an ancient bird, had hard, enamel-covered teeth.
2. Genetic evidence is consistent with developmental suppression
While the above studies focus on loss of function mutations, developmental biology also shows that parts of the gene regulatory network involved in tooth initiation (e.g., signaling pathways common to all vertebrate craniofacial development) are present but not expressed in ways that lead to complete tooth formation in birds. For example, signaling genes like SHH, BMPs, FGFs, and others involved in early tooth development exist in bird genomes and participate in other structures — but the downstream enamel and dentin formations do not proceed in avian embryos without specific genetic contexts. (General developmental biology consensus from genomic and embryological studies — comparable evidence often discussed in secondary sources like evolutionary developmental biology reviews.) Reddit
This pattern — genetic pathways present but suppressed or disrupted — is exactly what one would expect if the developmental program for teeth were “turned off” in evolution but left remnants in the genome.
Summary
Modern birds do retain genetic remnants of the biological systems for tooth formation, but these genes are:
- still present in the genomes of all living birds examined,
- inactivated or altered so they no longer produce the structures (enamel, dentin) needed for teeth,
- and remain potentially expressed in other developmental contexts.
In other words:
The information for tooth production exists at some level in bird genomes, but it is suppressed/dysfunctional in forming teeth today.
This supports the idea that tooth development is not completely absent, but rather developmentally switched off — consistent with gene regulation changes rather than the creation of new structures from scratch. PubMed
