The week between Christmas and New Year’s Day holds special significance for our family. It is the time of the year we clean and re-organize our garage. It has become a family tradition that no one really wants to celebrate.
As you can imagine, I dread cleaning out our garage for a number of reasons. For starters, I usually develop an allergic reaction to all the dust generated during the clean-up. I’m not alone. Nearly 1.2 billion people suffer from dust allergies. Usually, the symptoms are caused by house dust mites. These arthropods, which are related to spiders, feed on the organic debris (such as skin cells) that comprises a large proportion of household dust. These mites produce powerful enzymes that digest the keratin protein found in skin cells and hair. Scientists believe that these digestive enzymes are the real culprits, functioning as the primary allergens.
Even though these creatures are responsible for such wide-scale human suffering, biologists know little about how house dust mites relate to other mites. Many biologists think that understanding this evolutionary relationship would be helpful in addressing the medical problems caused by these creatures. To remedy this situation, a team of researchers from the University of Michigan (UM) carried out a large-scale study on the evolutionary relationships of house dust mites. To their surprise, the researchers discovered something completely unexpected: the evolutionary origin of house dust mites appears to violate Dollo’s Law.1
This law is a key tenant of the evolutionary paradigm, and its violation stands as another example of a failed prediction for the theory of evolution, adding to the list of reasons why I’m skeptical of the claim that evolutionary mechanisms can fully account for the origin, history, and design of life.
Most biologists believe the evolutionary process is irreversible. This idea is codified in what is known as Dollo’s Law, which was formulated in 1893 by French paleontologist Louis Dollo. This tenant of evolutionary biology states that an organism cannot return, even partially, to a previous evolutionary stage occupied by one of its ancestors. The genes and developmental pathways responsible for lost biological systems will eventually degrade because they are no longer needed. When genes are no longer needed, they are no longer under selective pressure.
Once free of the influence of natural selection, mutations in these genes will indiscriminately accrue to the point that the genes will become completely useless. These no-longer-needed genes are just like the stuff that accumulates in our garage. Eventually, my wife and I get rid of it because it is no longer of any use to us, but once our stuff goes in the trash or is carted off to Goodwill, there’s no getting it back.
House Dust Mite Origins Violate Dollo’s Law
In an attempt to understand the evolutionary history of house dust mites, the researchers from UM conducted a massive study examining the DNA sequences of five genes from 315 taxa of mites. They determined that house mites (which are free-living) evolved from parasitic mites that spent their entire lives associated with the hosts they infected. Their data show that these parasitic mite ancestors, in turn, evolved from free-living mites. In other words, when their origin is viewed from an evolutionary vantage point, house dust mites arose through a reversal of the evolutionary process. This result was so surprising that the UM researchers “decided to contact [their] colleagues to obtain their feedback prior to sending these data for publication.”2 Yet, the data generated by the UM researchers withstands scrutiny.
Parasites shouldn’t re-evolve the ability to exist as free-living organisms. Parasite genomes typically contain degraded genes and, in many instances, even lack genes that would be found in their free-living counterparts. Parasites thrive with reduced genomes because doing so exploits the biological resources provided by the host organism. Parasites no longer need many of the genes required by their free-living counterparts.
As the UM researchers point out, from an evolutionary vantage point: