Where Do House Cats Come From?

Question

Life Science Studies: Heredity, Genetics, and Variation in Traits

Scientists have discovered something new about the house cat, one of the world's oldest pets. The loving, aloof, graceful, and finicky ruler of millions of homes around the world is actually descended from the lybica, a Middle Eastern wildcat. Through DNA research, scientists have traced the house cat to five ancestors that lived many thousands of years ago in the Middle East.

The recent cat-origin study was funded by the National Institutes of Health and conducted by an international team of researchers. The team included Carlos Driscoll of Oxford University and the National Cancer Institute. Researchers collected information on mitochondrial DNA. Mitochondrial DNA is the substance that carries an organism's genetic information. Driscoll and the team tested the DNA of 979 domestic and wild cats from Europe, Asia, and Africa. They found that the DNA of some wild cats was identical to domestic cats in many parts of the Middle East. The discovery led the researchers to conclude that those Middle Eastern cats are related to the modern house cat.

"House cats, which includes fancy breeds and feral cats," said researcher Stephen J. O'Brien, "all form a genetic group that is virtually indistinguishable from ones in the Middle East."

The study traced the cats' ancestry to five types of wild cats that lived many thousands of years ago. These five types of cats interbred. This resulted in a new species, Felis silvestris lybica, the apparent ancestor of the modern house cat. At this point, said O'Brien, a cat version of "Adam and Eve" originated the species that would yield the house cat.

But how did the wild lybica become domesticated? According to O'Brien, the domestication of cats began just a few thousand years ago. The earliest archaeological evidence of cats and humans in association happened on the island of Cyprus. "We also have evidence of cat domestication by the Egyptians because of their . . . artwork," said Joan Miller of the Cat Fanciers' Association. Scientists have deduced that thousands of years ago, wild cats began hunting the rodents that plagued farms on which grains and cereals were grown. As a result, cats and humans developed a relationship.

"Domestication, for sure, took place in the Middle East where those cats live today," said O'Brien.

For O'Brien, the domestication of cats resulted from what he calls "an amazing experiment." He finds it extraordinary that an animal known for its ferocious and deadly nature was able to be domesticated.

Some are fascinated by a secondary finding of the research. While gathering DNA from European, Asian, and African cats, researchers found that some cats in the Middle East did not share the same DNA as the lybica. These cats were distinct from the species that yielded the house cat. "I would like to know more about these cats," said Joan Miller.

According to Carlos Driscoll, the study of cats is serious business for genetic researchers. Cats are a model for some human genetic diseases. The cat research is also expected to assist in wildcat conservation efforts.

Dig Deeper
DNA was key to discovering that house cats descended from Middle Eastern wildcats. That's because DNA is the information molecule. DNA stores information that a cell needs. This is how the cell can put together the correct sequence of amino acids needed to produce specific proteins. Proteins are large molecules. They are made up of chains of smaller molecules called amino acids. There are 20 different amino. These can come together in enough different ways to make up the thousands of different proteins found in the human body.

The DNA molecule is shaped like a double-stranded spiral. It looks something like a twisted ladder. Nucleotide subunits make up each of the two strands of the DNA molecule. (Nucleotides are subunits of nucleic acids.) One part of the nucleotide forms the side rail of the DNA "ladder." The other part, the nucleotide base, forms the rung. Actually, two bases come together to form the rung. Each nucleotide base attaches to another base from the opposite strand.

There are four different nucleotides in DNA. They are identified by their bases: adenine (A), thymine (T), cytosine (C), and guanine (G). There are differences in the size and shape of the nucleotides. Therefore, adenine always pairs with thymine (A-T). Cytosine always pairs with guanine (C-G). The bases fit together like two pieces of a jigsaw puzzle. These bases are often simply called by their initials—A, T, C, and G. Use the phrase "All Tigers Can Growl" to help you remember how they pair.

Diagram showing DNA molecule, eukaryotic cell with inset of DNA base pairs.

Image credit: Soleil Nordic/Shutterstock (DNA); Christoph Burgstedt/Shutterstock (cell)

A DNA molecule is a shaped like a double-stranded spiral, or double-helix, and is found in the nucleus of eukaryotic cells.

The sequence of bases in a strand of DNA forms the code for making proteins. Think of a list of ingredients in a recipe. In a way, a set of bases is like this. It lists the amino acids needed to form a particular protein. The cookbook uses just 4 bases—A, T, C, and G. These can code for 20 amino acids. A code of 2 bases to 1 amino acid gives only 16 possible combinations. However, a code of 3 bases to 1 amino acid gives 64 possible combinations.

The genetic code is, in fact, a triplet code. A specific sequence of 3 nucleotide bases codes for 1 amino acid. Three bases code for each amino acid. The genetic code, therefore, is called a triplet code. Each gene is made up of a sequence of bases. These are found at a particular location on the DNA.

According to the article, which happened after cats' mitochondrial DNA was tested?

They interbred to form a new species known as Felis silvestris lybica.
Their images were discovered in the paintings of ancient Egyptians.
Their ancestry was linked to an ancient wild cat known as lybica.
They developed a relationship with humans on the island Cyprus.

Answer 1

According to the article, after cats' mitochondrial DNA was tested, they interbred to form a new species known as Felis silvestris lybica.