This type of genetic change is not that uncommon; it has been estimated that some type of Robertsonian rearrangement occurs in 1 out of 900 human births. Because of the risks of birth defects and a general lack of reproductive success in individuals having an odd number of chromosomes, within a few generations the karyotypes tend to stabilize to the even numbers; in this case either 38 or 40. Because of this, Robertsonian rearrangements are viewed as a major factor in rapid species change. It also confuses biologists, making hybrid zones seem narrower than they really are. There can be a tremendous amount of introgression between two species having similar genetics but different karyotypes, but it is hard to see. A female jill might have 2 kits with 40 chromosomes, 3 with 38 chromosomes, and 3 with 39 chromosomes. Because the 3 kits with 39 chromosomes tend to have lower survivorships, when you sample the population, you mostly see polecats having 38 or 40 chromosomes, so hybridization appears to be less common than in reality. What this means in terms of domestication is that hybrid ferrets would also have karyotypes of 38, 39, or 40 chromosomes, but the ones with the odd number would tend to die out, either because of birth defects or a lack of reproductive virility. Descendents of these hybrids would therefore tend to have either 38 or 40 chromosomes. Continue to breed those descendants to European polecats, and in a surprisingly short number of generations, most of the descendents would have 40 chromosomes even though they have genes from both polecats. Reverse it by breeding to steppe polecats, and the karyotype would tend to stabilize after a number of generations at 38 chromosomes. This is why it is a mistake to try to use the karyotype of the domesticated ferret to determine the ancestral progenitor. All you are looking at is the last few hundred years of breeding practices, not necessarily true ancestral origins. The actual genetic structure of the two species is quite similar. Geneticists can find genetic differences between the two polecats, but the real question isn't one of differences. Rather, it is one of similarities. For example, a lot is made of the differences in culture between European Americans and African Americans, and a number of real differences exist. The question is, are those differences significant? If you are a separatist, you say they are, but that is an arbitrary distinction, not a scientific one. A better way of looking at the distinction is to measure the degree of variation with European American culture, that within African American culture, and that between European American and African American cultures. When you do it that way, you discover the differences between cultures are less than those within cultures. In other words, there are more differences within the European American culture than there are between European American and African American cultures. So, now how different are they? That is the problem when defining a species. When you measure the variation within European polecats and steppe polecats, then measure the difference between the polecats, you discover there is more variation within the groups than between the groups. In other words, they are far more alike than they are different. These findings have been confirmed in several genetic studies, suggesting the two species of polecats are genetically quite similar. Paleontology also confirms the close relationship of the polecats, suggesting the separation between species is less than 500,000 years. The willingness and commonness of hybridization also suggests a very close relationship. The more the relationship between the polecats is studied, the more the distinction becomes blurred. If the distinctions between the polecats are blurred, how easy can it be to determine which polecat is the ancestor of the ferret? This is why the authors of recent genetic studies clearly stated they could not determine the progenitor of the ferret. The authors of the genetic studies went a step further than just suggesting the ancestor of the ferret was unknown. The suggested reason suggested for the difficulty of progenitor determination was introgression; that is, hybridization. In other words, the reason given for the difficulty of finding the ancestor of the domesticated ferret was that it had been bred back to the two polecats so frequently that it made the distinction too hard to resolve (at least with the research methodology used). If genetic studies cannot help us to determine the ancestor of the ferret (at least at this time), what other lines of evidence can be used to determine the progenitor? Historic records can be of some value. If you look at the oldest possible references of the ferret, those from Aristotle, Aesop, and Aristophanes, they are all Greek. All three authors use the term "Iktis" (or Ictis), which has been translated as polecat, weasel, marten, house-weasel, and ferret, depending on the translator. No one is really sure of what animal Aristotle is talking about; a polecat, marten, mongoose, or ferret--it is hard to tell, although linguistic evidence suggests it is probably either a polecat or ferret. You can argue this because both Aesop and Aristophanes use the same word in their writings and it is unlikely that the word would have shifted meaning in such a short period of time. The translation in Aesop's writing is confusing because of the tendency of medieval period writers to change the animals mentioned in the fables to those of a biblical nature, so in many modern translations you see "asp" or "fox" in places where iktis was originally penned. In the most modern translations of Aesop from the Greek, iktis is translated as "house-weasel" or "house-marten." Of the three, Aristophanes is the most meaningful because of the nature of the writings. Aristophanes was a popular playwright and political satirist. Aristophanes used iktis in at least 4 surviving plays to describe an animal that was associated with people and their homes, an animal that was known for it's odor, and who would steal food. The animal was common enough for people to be able to recognize the satirical reference, so the implication is the animal was common, recognizable, and kept in homes. Later references to the word iktis invariably refer to the polecat or ferret, so linguistic continuity suggests the word is referring to either the ferret or the polecat. The classic objection to using the early Greek writers to support an early ferret domestication is that in later writings iktis is used to name the polecat. On the surface, this would be a valid objection; early writers used iktis for polecat, later writers used iktis for polecat, how can it be used for ferret? However, the objection ignores the time it takes for new words to be invented to replace the existing names in the everyday vernacular. For example, the names of both domesticated and wild forms of mice, rats, chinchillas, hamsters, gerbils, skunks, mink, rabbits, and fox are exactly the same, even though the domesticated forms are clearly domesticated, and some have been for centuries. Also, some languages conserve the basic form of the word, using prefixes or suffixes to modify it for greater understanding. For example, in Hungarian the word "gvriny" means polecat, "vadaszgvriny" means domesticated ferret, "feketelabz gvriny" means black-footed ferret, "molnargvriny" means steppe polecat, and "tigrisgvriny" means vormela (AKA: the tiger or striped polecat). Gvriny has been conserved and is interchangeable with ferret or polecat, essentially meaning both. It is the prefix that defines the way the word is to be interpreted. One of the reasons you know the ferret has had a long domestication history is because it has a different name than the polecat. To the ancient Greeks, ferret domestication would have been comparatively recent; it would not be surprising to find they used the same word for both polecat and ferret, allowing the context of the message to define the exact meaning of the word. [Posted in FML issue 4730]