Silver Foxes Change Rapidly… and in Surprising Ways

In the experiment, farm-bred silver foxes went from being agressive towards people (left) to being friendly (right) in as little as six generations. (Photos from reference 1)

I recently read about a fascinating experiment that has been going on in Russia for the past 50 years. Dmitry K. Belyaev acquired some silver foxes from a farm that breeds them for their fur. The farm started about 50 years prior to the experiment, so several generations of foxes had experienced human contact to some degree. However, the foxes still did not care for human contact and were quite aggressive if they were forced into such contact.

Belyaev took this group of foxes and began trying to develop a new trait: tameness. Each fox was exposed to a human for a specific amount of time at specific ages. The fox was then evaluated based on how well it reacted to the human, and only the foxes with the best overall reactions to humans were bred. In a mere six generations, some foxes were born that not only enjoyed human contact, they actually craved it! This behavior became characteristic of the entire population, so that the foxes now behave like dogs – wagging their tails, whimpering, licking people, and generally doing all they can to interact with people.1

Now these results are cool on at least two levels. First, I was shocked at how quickly the foxes adapted to human socialization. For human-friendly foxes to appear in a mere six generations just astounds me. I know that dogs were domesticated from wolves, but I always imagined that it took a long, long time. After all, a lot has to change in order to take an animal that avoids people and is aggressive towards them and turn it into an animal that not only jumps up on your lap to cuddle with you but begs to be able to do so! According to this experiment, however, the change can happen quickly. Second, I just think it would be incredibly cool to have a pet fox. From time to time, I see a wild red fox in the neighborhood where I live. I would love to have such a beautiful animal as a pet!

Those are the cool aspects of the experiment. However, there are a lot more interesting aspects to the experiment, and they indicate that we still have a lot to learn when it comes to genetics.

You see, while the experimenters selected for one trait and one trait only (tameness), the new population of silver foxes is different from the original population in many other aspects, and it is not clear how those aspects necessarily relate to tameness. In order to make this experiment a bit easier to discuss, I want to define two terms for you. Genotype refers to the genetic makeup of a given organism. Phenotype, on the other hand, refers to the observable characteristics of a given organism. For example, before I started going gray, I had dark brown hair. That’s my phenotype. The reason I have dark brown hair is because of specific genes that I have. If I listed all the genes that make my hair dark brown, that would be the genotype that leads to my phenotype of (formerly) dark brown hair.

In the case of this experiment, the only phenotype that was selected for was tameness. It turns out that in a subsequent paper, the scientists involved in the experiment located two sections of the fox DNA that seems to have changed remarkably from the original population.2 While the specific genes involved in this change have not been identified, when they are identified and characterized, we will have the genotype that is associated with the phenotype of tameness.

Here’s the interesting part: While the only phenotype being selected for is that of tameness, other phenotypes have arisen that are quite different from the original population. To me, the most interesting one had to do with reproduction. Wild silver foxes mate early in the year, in response to increasing daylight hours. They do not breed at any other time of the year. Silver fox farmers have long tried to change this so that they can produce more foxes, but they have never been successful. In this experiment, however, many of the foxes now breed at different times of the year, and some have even mated twice in the same year. By selecting just for tameness, somehow the experimenters have been able to produce a reproductive change that silver fox farmers have been trying to make for many years!

Other changes have been seen as well. Certain hormone levels are significantly different from the original population, and the pups reach sexual maturity about one month earlier (on average) than the original population. In addition, they have (on average) one more pup per litter. Once again, these are phenotypes that would be very valuable to fox farmers, but they were not produced by selecting for such phenotypes. Instead, they were produced by selecting only for tameness.

Another mysterious phenotype that has become more frequent is a specific pattern of white spots on the head that is referred to as “Star spotting.” The spotting pattern appears in farm-raised foxes, but at a very low rate (about 71 in every 10,000 foxes). In the current population of tame-bred foxes, the pattern shows up in just over 12% of the population. Once again, then, by selecting only on the phenotype of tameness, the experimenters have increased the frequency of a seemingly unrelated phenotype by more than a factor of 17! There were other phenotype changes as well, but I think you get the idea.

So what does all this mean? To one extent, it just confirms what we already know. Very few genes affect only one trait. Instead, most genes affect a variety of traits. We call this pleiotropy, and it means that when you make even a small change to the genotype of an organism, you will probably see lots of changes in the organism’s phenotype. However, there has always been a thought that the phenotypes which are affected by a specific genotype are at least partially related to one another. This experiment shows that’s probably not the case. While hormone levels would be expected to change as a result of selecting the tamest foxes, you would not necessarily expect breeding patterns, fertility, and coat coloring to change. Nevertheless, they all did. That tells us we still have a lot to learn about how the DNA of an organism relates to the various characteristics that organism possesses.

It also tells us that these changes can occur rather rapidly. Look at the picture that appears on top of this post again. It took only a few generations to make that change in some members of a population, and it took only 50 years to make the change throughout the entire population. That tells us populations can change rapidly, given the right kinds of selection. This is precisely what young-earth creationists believe. In order for the animals on the ark to diversify and produce the variety we see today in the various kinds of animals God created, populations must be able to change rapidly, given the right kinds of natural selection. This experiment using artificial selection provides evidence the young-earth creationist view is correct on that point.


1. Trut L, Oskina I, and Kharlamova A, “Animal evolution during domestication: the domesticated fox as a model,” Bioessays 31(3):349-60, 2009.
Return to Text

2. Kukekova AV, et. al., “Mapping Loci for fox domestication: deconstruction/reconstruction of a behavioral phenotype,” Behavioral Genetics 41(4):593-606, 2011.
Return to Text

20 thoughts on “Silver Foxes Change Rapidly… and in Surprising Ways”

  1. I don’t know whether this was controlled for, but it is possible that there are connections between the phenotype changes recorded in the human half of the interaction. For example it may be that humans consider Star spotting attractive and therefore (most likely subconsciously) treat foxes that manifest that characteristic better than those that have plain fur. This attention difference may improve the relationship between fox and human and therefore be related to tameness.

    1. That’s an interesting idea, Josiah. They tried to make the evaluations as analytic as possible, but obviously there is no way to make them totally unbiased. Also, evaluations were made at several different stages of the animal’s development. I don’t know when the spotting occurs in the fox’s lifespan, but I would think that this would at least mitigate such a bias. Nevertheless, your point is very well made.

  2. Fascinating! Thank you for the article! It makes me wonder how human cultural trends affect the genetics of their descendants. I would like to see a study done on that.

    1. Enoch, there have actually been some studies on that. For example, we have a digestive enzyme in our saliva called amylase. It is used to start the digestive process for certain carbohydrates, especially starch. Well, it turns out that the number of copies you have of that gene affects how much amylase is in your saliva – the more copies you have, the more amylase there is in your saliva. When people in cultures that have low-starch diets are compared to people in cultures that have high-starch diets, geneticists find that the people in high-starch-diet cultures have a larger number of copies of the gene that produces amylase. It is assumed that this is an example of how a culture’s trend has affected its average genome.

    1. Thanks for the link, J.S. If Joshia is still following this thread, he should read the article. It bolsters his view that the Star spotting that shows up in the silver foxes is an inadvertent consequence of people liking such novelty. According to the article, that has been shown to be the case in pigs:

      In 2009 Andersson bolstered his theory by comparing mutations in coat-color genes between several varieties of domesticated and wild pigs. The results, he reported, “demonstrate that early farmers intentionally selected pigs with novel coat coloring. Their motivations could have been as simple as a preference for the exotic or selection for reduced camouflage.”

  3. I always follow the threads Doctor. At least, until they get hideously long and complicated.

    I actually think the most interesting thing in that article however, aside from the prospect of having a pet fox, is the genetically horrid animal raised by a tame mother. It is really quite scary how much behaviour seems to be determined before the creature is even born.

    1. I guess I don’t find that scary, Josiah. Especially for animals, I would expect an enormous amount of the behavior to be determined by genetics. I would hope that it is less in people, but even in people, I would still bet that a large amount of a person’s behavioral tendencies are determined by genetics. One difference between people and animals is that we can choose to ignore our behavioral tendencies.

  4. I wonder just how much this same type of experiment could apply to larger wild cats such as tigers and lions. Could selective breeding possibly lead to wild tigers and lions being completly tame? There are obviously massive differences between foxes and tigers and lions, namely different animal group and size!! I could imagine a conversation between two researchers, “So, I want you to go in there and find out which one responds the best to your touch.” “Ummm, how about you go in? You’re the head of the project!!” I’ll put in my two cents about the behavior tendencies and why I personally don’t think they apply to humans in the same way. Before I became a christian I had the tendency to want to beat up mostly every guy that had even the slightest meanness toward me and I thought about fighting and hurting other people all the time, I literally thought that this was just the way I was built, there was no way I could help it. As soon as I came to Christ, my behavior radically changed to gentleness and kindness, as if I became a totally new person. This is why I think that “the genes made me do it” similiar to “the devil made me do it” is not a good approach, thus why I don’t really find it scary at all from a human perspective. In my opinion, based on personal experience, humans can radically transform, I’m one of them.

    1. Eric, I am not sure whether or not this kind of experiment would work on lions and tigers, but I wouldn’t be surprised if it did. There are a couple of videos (here and here) that show that some individual lions can be rather tame. Thus, I would think such behavior could be selected, although I agree that the initial tests might be rather hard to do! I would also think that if this process worked, it would be quick, as genomes do seem to have the ability to change quickly, given the right kind of selection.

      In terms of behavior, one could speculate that your new behavior is a result of the Holy Spirit working against your genetic tendencies. Thus, I am not sure that your experience necessarily indicates that behavior isn’t influenced by genetics. I agree that the “my genes made me do it” defense is wrong, but that’s specifically because as people, we can fight genetic tendencies in our behavior.

      Thanks for the link. The geological formations are pretty cool, but I do like to keep the threads at least somewhat related to the original post.

  5. Dr. Wile, Yes, you’re right, I have seen some of the dialogues that went on in some of your other posts and they can get rather off topic, I’ll keep it to the point then.

  6. First off I need to tell you how much I enjoy your blog–I so look forward to your posts! This post about the foxes is so interesting. I wonder if we are looking at current aggressive animal behavior correctly. If Adam was given dominion over all the creatures, maybe we shouldn’t be surprised by this tameness trait being “rediscovered.” Maybe our current experience of aggressive behavior is the result of adaptation to human abdication of proper dominion relationships with the animals. If it only takes 6 generations to reclaim this trait, maybe it only took a few generations to bury it as well. Just a thought.

  7. Umm, Jay, you forgot to mention how sin fits into this story.

    You know, like how sin is responsible for the common problems associated with the human appendix. Including killing people.

    So surely sin must be responsible for making foxes mean in the first place, right?
    So, do foxes sin? And are they saved by the precious blood of the barbaric human sacrifice of Jesus?

    1. L.W., you probably should have read the thread before posting your comment. The effect of sin has already been discussed in the thread. And no, foxes do not sin. All of creation, including foxes, suffers because of the Fall (Romans 8:19-21). Since animals don’t sin, they don’t need the atonement of Christ’s blood. Only people need that. You might think the sacrifice of Jesus is barbaric, but it is the ultimate expression of love. God loved us so much that he gave us his only son (John 3:16)!

  8. Now that L.W. has commented on how sin could tie in with this, what you said about the genetic behavior tendencies being controlled, altered by the holy spirit would have strong support. “The fruit of the spirit is love, joy, peace, patience, goodness, kindness, faithfulness, GENTLENESS, and SELF CONTROL.” If your behavioral tendencies were effected by your DNA, and caused you to be naturally meaner and more aggressive, the holy spirit could effectively give you Self Control and Gentleness, so I am in agreement that it would be the property of the holy spirit working against genetic tendencies, as the apostle Paul says, “For the Flesh desires what is contrary to the Spirit, and the Spirit what is contrary to the Flesh. They are in conflict with each other, so that you do not do what you want..” Galatians 5:17

  9. A barbaric human sacrifice as the ultimate expression of Love?

    That may well qualify as the single most vile, sickening, appalling,revolting, sadistic,evil, wicked idea that the human mind has ever concocted in our entire history on this planet.


    1. L.W., you seem to be very angry at God – so angry that you can’t understand His ultimate expression of love. Perhaps reading The Rage Against God will help. Peter Hitchens discusses this kind of anger and its source.

  10., I will add an additional source that I have found that takes a very thorough look as to why God had to do what he did. L.W., take the time to read through it and see if you still believe that Jesus sacrifice was immoral. If you do, come back with some reasonable arguments that would support your position.

Comments are closed.

%d bloggers like this: