Did your cat evolve to like you?
Feral felines and domestic cats are all capable carnivores. Scientists have now identified some of the genes that equip them to be great predators as well as genes that make domestic varieties content to share your affection and your home with your dog. (Perhaps I need to share this study with my dog, who is less than pleased with the arrangement.)
Geneticist Michael Montague and colleagues compared the genomes of domestic cats to wildcats. They examined the genomes of 22 different domestic cats from around the world and 4 wildcats (2 European wildcats and 2 Eastern wildcats). They also compared these cat genomes to the genomes of tigers, dogs, cows, and humans.
Since all of these are mammals designed to live in the same world, it is not surprising that they have many genes in common. The authors focused their attention on 467 genes that the carnivores in their sample shared and examined how much they varied. Though this study did not assess the functional significance of specific genetic differences, the assumption was that greater genetic similarity was evidence that those genes likely provided some sort of advantage that had been positively selected to persist in that population. They found that 331 of the 467 carnivore-associated genes were very similar among all of the cat genomes surveyed. And 281 of these genes were particularly similar among all the domestic cats, highlighting the genetic variations likely responsible for many of the unique qualities—physiologic, anatomic, behavioral—of the domestic cat. In other words, they think they found the genetic underpinning that makes the sweet kitty you’d give your child as a more suitable pet than a wildcat.
Through their genomic comparisons, the researchers found clues to explain how today’s cats, obligate carnivores, thrive on a diet typically so high in fat that a human consuming it would be at great risk for coronary heart disease. They discovered the genetic differences that make dogs more reliant on smells for hunting and cats, on sound. They identified the genes likely responsible for a cat’s exceptional visual acuity and night vision. They even found the genes that influence common coat patterns seen in domestic cats and the genes that equip domestic cat species to be agreeable pets.
Cats are all in the family Felidae. There are about 38 species including lions, tigers, wildcats, and of course the domestic cat (Felis silvestris catus). Modern cats generally need meat in their diet, as they—unlike other mammals—are unable to synthesize the organic acid taurine themselves. Fat metabolism in cats also differs from that of other mammals. The researchers noted that an unusually large portion of the unique parts of the cat genome is associated with fat metabolism. They conclude, “The enrichment of genes related to lipid metabolism is likely a signature of adaptation for accommodating the hypercarnivorous diet of felids, and mirrors similar signs of selection on lipid metabolic pathways in the genomes of polar bears.”2
To say “enrichment” here implies the genes were added to the evolving genome inherited from some less carnivorous non-cat (or non-bear) ancestor. There is no evidence that that happened nor any known mechanism whereby it could. Though the large number of genes related to fat metabolism may equip cats (and polar bears) to cope with a high fat diet, they did not acquire those genes through adaptation but rather are able to adapt to such a diet because they already have the genetic variations.
To hunt, dogs rely more on their noses than cats do. This distinction seems to be reflected in their genes. Dogs have at least a hundred more genes devoted to olfactory sensation than cats. Cats, on the other hand, can hear a broader range of frequencies than any other carnivores, making them able to detect tiny movements of their prey and even ultrasonic communication between other animals. The researchers found six cat-specific genes associated with auditory acuity and range. (They were able to identify this probable role for these genes because mutations in them typically produce hearing deficits.) Excellent vision is also important for a good hunter, and the carnivore genomes examined in the study had in common 20 genes thought to be associated with visual acuity and night vision.
Of particular interest to cat lovers, of course, are the factors that make the domestic cat suitable as pets. Indeed, even Darwin puzzled over what could make some animals more easily domesticated than others. After all, while any number of animals might learn to hang around humans to grab some easy meals, being domesticated requires them to overcome a certain amount of fear and to learn to respond to rewards, particularly edible ones. The researchers consider cats even now only “semidomesticated” because humans do not control the breeding and food supply of the domestic cat population to the extent we do with dogs and other domesticated animals.
Wildcats are thought to be the immediate ancestors of domestic cats. Domestic cats are smaller, less robust, and have comparatively smaller brains and shorter legs. Evidence suggests that cats have been domesticated, to some extent at least, for thousands of years. Archaeologists have found a cat carefully buried beside a human in a Neolithic gravesite at Shillourokambos on the island of Cyprus.3 A domestic cat is pictured with a rodent in ancient Egyptian art of the Middle Kingdom’s 12th Dynasty. And archaeological evidence shows domestic cats coexisted with people in a central Chinese agricultural village thousands of years ago.4
While dogs and other domesticated animals have long been bred to perform various functions, anthropologists suspect cats became “semidomesticated” after they made themselves welcome and useful in farming communities. Evolutionary anthropologists frequently make worldview-based assumptions that agriculture had to emerge as humans evolved greater intelligence, but that is a view fraught with many errors. Read more about how archaeological findings and God’s Word actually agree on this matter in “Archaeologists Find Farming’s Roots All Over the Fertile Crescent.” Nevertheless, there is no reason to doubt that cats predisposed to adapt to a domestic life may have begun their path to domesticity by making themselves useful in the many agricultural settlements that developed after the global Flood.
Examination of the collagen in those ancient Chinese cats suggested their diet contained both meat and millet, which scientists interpret as evidence they made themselves useful by keeping down the population of grain-ravaging rodents. Additionally, one of the ancient Chinese cats was older than others found in the village, and it appeared to have subsisted on a diet heavier in millet than the others, leading to suspicion that it may have been someone’s pet. But was there something about the cats that people domesticated that made them especially suited to life among humans, leading to their emergence as a separate species?
The scientists found that domestic cats have 13 genes whose variants (alleles) are distinctly different from those genes in wildcats. Some of these variations are known, based on experiments with mice, to affect fear, memory, and the ability to learn by responding to rewards. “That jibes with what we know about the domestication of cats,” Montague explains, “because they would have needed to become less fearful of new locations and individuals, and the promise of food would have kept them sticking around.”
Domestic cats not only behave differently from wildcats but also look a little different. These differences may well be regulated by cells in the embryo that act like master control switches affecting brain size, hair length, texture, and coat patterns. Five genes that have variants common in domestic cats that are known to influence the migration of these regulatory “neural crest cells.” Such genetically regulated switches may affect many traits, producing clusters of qualities we associate with domestic animals. Domesticated dogs share many more genes than domestic cats. The researchers point out that this may be as a result of their long history of selective breeding for particular functions. Perhaps it also reflects the generally independent spirit most of us associate with the cats compared with the dogs in our lives.
But does anything about this study support molecules-to-man evolution? No. Does any of this reveal that all carnivores share a common ancestor? No. There are many kinds of carnivorous animals, and they do not share a common ancestor. In fact, their various ancestors (plural) were not (Genesis 1:29) originally even carnivorous. According to God’s Word, about 6,000 years ago God created all kinds of animals during Creation Week. He created them fully functional and able to reproduce after their kinds. Thanks to the genetic information God put into each kind of animal, they are able to vary a lot but only within each created kind. This is exactly what we observe in biology.
Today, to determine just what the original kinds of animals were like, biologists look at their characteristics as well as what sorts of animals are able to breed with each other. Answers in Genesis in conjunction with several outside scientists has been conducting research and review of the biological literature in order to determine this information, and the Answers Research Journal has published this information in articles such as “Mammalian Ark Kinds.”
In her analysis, Dr. Jean Lightner reports, for instance, that all cats—lions, tigers, and house cats included—are all best considered as variations of one created kind. They are all in the family Felidae. Felidae has two subfamilies, but members of these two subfamilies are known to hybridize.
The fact that all cats—big and small, cuddly and fierce—are varieties of the same created kind is also backed up by genetic evidence. (You can read more about it in “Extinct Carnivore Ancestor of Lions and Tigers and Bears? (Oh My!).") Thus, based on this evidence and the testimony of Genesis 1, we strongly suspect that God created one kind of cat and that the varieties we have today descended from it. This is what we mean by variation within a created kind, and it is not the same thing as molecules-to-man evolution.
There is no biological evidence for the divergence of canines, cats, and bears from a common carnivorous ancestor. Or even for their divergence from a common ancestor of any dietary preference, for that matter. Biological observation reveals that animals reproduce and vary only within their created kinds, so there is no scientific justification for insisting that in the unobservable past they evolved into more complex and divergent kinds of animals from a common ancestor.
Bible-believers will agree that the cat has changed: from its created herbivorous state , the cat kind at some point became dependent on meat for two essential components of its diet—taurine (described above) and vitamin B12. The Bible clearly teaches that our world “red in tooth and claw”5 only became violent after man sinned, so how did the original kind of cat—which was not carnivorous—get the vitamin B12 and taurine it needed? Answers in Genesis molecular geneticist Dr. Georgia Purdom explains how feline dietary requirements could have eventually changed in the sin-cursed world following the rebellion of man against God:
Some animals (like herbivores) possess bacteria in their rumens or gut that synthesize B12. Vitamin B12 is involved in many aspects of cellular metabolism, especially DNA synthesis. Possibly all animals and humans originally had symbiotic bacteria in their gut that synthesized B12 (this relationship was altered following the Fall). It is also plausible that pre-Fall/pre-Flood plants had levels of taurine and B12 that met the requirements for the cat kind. Degenerative mechanisms, such as mutation following the Fall, or plants going extinct may have led to changes in the nutritional quality and availability of plants, making meat a necessary part of the cat kind diet.6
It’s fascinating to learn the genetic basis for the biodiversity we see in today’s world, and perhaps even more so to discover the basis for traits we value highly and enjoy. That such biodiversity has developed in animal populations in the post-Flood world is in some measure a reflection of God’s mercy on us even after judgment in this sin-cursed world.
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Nature is “red in tooth and claw.” This phrase comes from Alfred Lord Tennyson’s lengthy elegy to his friend, “In Memoriam A. H. H., 1850.” In Canto 56 Tennyson describes what many people see as a conflict between the loving character of God and the suffering surrounding us in the world. He wrote:
Who trusted God was love indeed
And love Creation’s final law
Tho’ Nature, red in tooth and claw
With ravine, shriek’d against his creed.
The Bible provides us with the answer—on God’s own authority—to Tennyson’s concern. That answer lies in our history. Death and bloodshed and suffering and carnivory exist as a result of mankind’s rebellion against God. The Bible’s book of Genesis tells us that God originally created a perfect world in which animals were vegetarians. After Adam and Eve rebelled against their Creator, God judged that they would eventually die, and that same curse affected the world that God had created for them. Had Adam and Eve not sinned, we would not be talking about the origin of carnivory. We would only be talking about the various kinds of vegetarian mammals that God created in the very good world about 6,000 years ago. Read more about the origin of death and suffering in Dr. Terry Mortenson’s detailed explanation, “The Fall and the Problem of Millions of Years of Natural Evil.”