Genetic evidence that whales lost a complete organ in their evolutionary past

The vomeronasal organ is used for chemical detection in many vertebrates. It is similar to smell, but it usually functions in pheromone reception. Pheromones are chemicals produced by animals that are used to communicate with each other, for example in their urine.

snake

Snakes flick their tongues to gather chemicals in the air to pass over the entrance to their vomeronasal organ.

800px-Flehmendes_Pferd_32_c

Horses and cats exhibit the flehmen response to gather airborne molecules for their vomeronasal organ

McGowen et al. [1] highlight the fact that extant whales completely lack a vomeronasal organ. As I described in a previous post, early fossil whales showed evidence of a vomeronasal organ (i.e., the presence of incisive foramina), which is consistent with its presence in other hoofed mammals, but this was lost by the time Remingtoncetus appeared approximately 48.6-40.4 million years ago. This makes sense because the vomeronasal organ, as well as smell, generally work best with airborne molecules rather than molecules dissolved in water.

If the vomeronasal organ was lost during whale evolution, it would suggest that the genes crucial for vomeronasal organ function have been rendered pseudogenes in whales. In fact, the bottlenose dolphin possess 36 V1R pseudogenes, genes that formerly would have ‘captured’ odors to induce electrical signals to the brain. Another vomeronasal gene, TRPC2, is exclusively expressed in vomeronasal neurons. This is not only a pseudogene in the bottlenose dolphin (toothed whale) and the fin whale (baleen whale), but the pseudogenes of these two species share the same inactivating mutation. This implies that this gene was inactivated prior to the last common ancestor of modern whales, a feature that is consistent with the fossil record.

Questions for Creationists

Why might God have created whales with vomeronasal pseudogenes? If the vomeronasal organ is entirely absent, would it not have made more sense to create whales without remnants of these genes? Is it a coincidence that a baleen whale and toothed whale share the same inactivating mutation in a vomeronasal gene? Is it also a coincidence that this shared inactivated mutation is consistent with the fossil evidence for vomeronasal organ loss in whales?

References

1. McGowen, M. R., Gatesy, J., & Wildman, D. E. (2014). Molecular evolution tracks macroevolutionary transitions in Cetacea. Trends in ecology & evolution29(6), 336-346.

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One thought on “Genetic evidence that whales lost a complete organ in their evolutionary past

  1. Pingback: When whales walked: Fossils document the rise of the largest animals on earth – Evolution For Skeptics

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