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Our kinship with cats or dogs is a matter of perspective.(Image credit: Anastasiia Krivenok via Getty Images)Share this article 0Join the conversationFollow usAdd us as a preferred source on GoogleSubscribe to our newsletter
They occupy our beds, pilfer our meals, and generally hold dominion over our homes. Collectively, cats and dogs account for two-thirds of pet ownership globally. But between these two cherished companion species, which one shares a closer lineage with us?
The response hinges on the lens through which the question is viewed.
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Cats, dogs, and humans all fall under the classification of mammals. Within the mammalian family tree, which illustrates the relationships between different mammal species, both felines and canines belong to the order Carnivora, whereas humans are categorized as primates. These two branches diverged from a shared ancestor approximately 90 to 95 million years ago, according to Springer. In contrast, cats and dogs diverged from each other much more recently, around 55 million years ago.
In terms of shared ancestry, “dogs and cats are more closely related to mammals like pangolins, horses, cows, whales, bats, shrews, and moles than they are to humans,” Springer explained. Furthermore, “humans are more closely related to colugos [flying lemurs], tree shrews, rabbits, rats, and mice than they are to cats and dogs.”
Genetic Ties
An alternative method for determining our closest species involves a genetic examination.
When assessing the extent of DNA code alterations over time, humans exhibit roughly equal relatedness to both cats and dogs, as communicated by William Murphy, a comparative genomicist at Texas A&M University, via email to Live Science.
However, a distinction emerges when scientists compare the organization of DNA strands within chromosomes.
Murphy elaborated that the predecessors of contemporary dogs underwent significant chromosomal rearrangements throughout evolutionary history. (Such rearrangements are not exclusive to dogs; they occur across various animal and plant species, although the precise reasons for faster rearrangements in certain lineages remain not fully understood by scientists.) Conversely, cats have maintained a genome organization that bears a closer resemblance to ours. “Regarding the arrangement of genes within chromosomes, humans and cats exhibit twice the similarity to each other compared to humans and dogs,” he noted.
Humans and cats share twice the similarity in gene arrangement within chromosomes compared to humans and dogs.
(Image credit: wildpixel via Getty Images)
Given that genome organization influences how genes are activated and deactivated, cats might serve as a more effective model than dogs for comprehending human gene regulation, according to Murphy.
This also renders them valuable for investigating genetic ailments. For instance, polycystic kidney disease affects both humans and cats, and therapies developed for felines could offer insights for human treatments.
Cats may also provide revelations regarding cancer. A recent investigation discovered that cancer-associated genes in cats bear a striking resemblance to those in humans, both in quantity and variety. A notable illustration involves a gene named FBXW7, which exhibited mutations in over half of the feline mammary tumors examined. In humans, alterations in this same gene are linked to poorer prognoses in breast cancer.
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Nevertheless, dogs are also utilized to model and analyze human conditions, including Alzheimer’s disease, idiopathic epilepsy, various eye diseases, and cardiovascular ailments.
While cats may exhibit greater genetic alignment with humans in terms of gene regulation, a larger body of research has, to date, been conducted on dogs. This could be partly attributed to the fact that the complete feline genome became accessible later than the canine genome, as well as historical biases—cats have long been perceived as less amenable to research settings.
So, to which species are we more closely related? From an evolutionary perspective, it’s a draw. Genetically, however, particularly concerning genome structure, we are more akin to cats.
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