Fluffy’s Feline 19-and-Me*

July 15, 2025

Kate Preston

The next time your playful Fluffy nips you with those pointy little teeth, it may be a sharp reminder that Felis Catus/Felidae/Mammalia evolved from a long, long line of life forms going back to a multi-celled chordate creature (a life form with a spine), c. 320 million years ago (“mya”).  Mammals did not really begin to develop until the Paleogene Period, c. 66 mya, the beginning of the current Cenozoic Era.¹

Fluffy Climbs the Family Tree

Fluffy’s distant ancestors lived during the Mesozoic Era, when dinosaurs ruled the earth. Throughout that time, vertebrates called therapsids (mammal-like reptiles), ranging from the size of a rat to over a ton, evolved and coexisted with dinosaurs.² Almost all of these creatures, including those we now call Tyrannosaurus Rex and Brontosaurus, fell victim to a mass extinction event. Geologists theorize that this deadly event of 250 mya may have been caused by a series of giant volcanic eruptions in Siberia over a period of two million years, covering a land mass the size of the United States – and filling the sky with particles blocking light and heat. The Mesozoic Era ended with this near-total extinction, and the earth remained much colder and darker than before for a few ensuing millennia.

The Cenozoic Period ushered in the “Age of Mammals,” when creatures that evolved from the Mesozoic survivors adapted to changing circumstances. It is in the Cenozoic Era, starting about 66 mya, that we find the real beginnings of the feline family (the “Felidae”), including today’s domestic cat, Felis Catus.³ Nature’s early tentative attempts at mammalian life introduced fur to counter the cold better than scales; omnivores that consumed other life forms as well as plants; and teats and live births rather than eggs to procreate.

Most of these Cenozoic creatures would look quite alien to us today, but “among the prominent carnivorous mammals of the time [was] a group known as the creodonts, [which] ranged in size from that of a small cat to lion- or bear-size species, and often converged in appearance with those animals.”⁴

Creodonts could be separated into two groups: a slightly cat-like variation (such as Sarkastodon, the largest Oxyaenid) found in North America and Europe, and a vaguely canine version (Hyaenodon) found in Africa, Eurasia, and North America. Some taxonomists believe there is a relationship among weasels, bears, foxes, etc., and have included these in genetic subgroups. Zoologist Christopher Taylor demurs, writing, “…  there’s just one small problem – there’s not a shred of evidence to support it.”⁴ In short, creodonts may have looked vaguely like these contemporary mammals, but scientific examination suggests appearance may not tell the true story.

The correct nomenclature for species that seem related by appearance is determined by skeletal factors such as dentition, paw/hoof configuration, and ankle- and wrist-type bone structures. The classification conflicts arise from different interpretations of fossilized remains. These tell how and what the animal ate, how it moved, and what survival qualities it inherited and passed on to its young.

Another Cenozoic group, the Miacid class, possessed qualities of both small and big cats closer to felines as we know them. The Miacids also exhibited heterodont feline dentition,⁵ possessing a variety of tooth shapes – some for tearing, some for crushing. The more primitive homodonts had only one kind of tooth, often just incisors for tearing, like today’s alligators and sharks. Heterodonts can consume a broader array of edibles than homodonts.

So … Where did Fluffy get his heterodont feline genes? And how did those genes develop into Fluffy? Let’s start with what creodonts ate and how.

Dramatic Diversions

“The earliest creodonts had teeth like living possums and probably ate a variety of meat, insects, and plant material. Later forms … had powerful jaws and tightly interlocking teeth and were probably powerful carnivores like the living wolverine.”⁶

Fearsome dentition was perhaps the most distinct feature of fossil remains of one extinct descendant of creodonts: the Smilodon, or “Sabre-toothed Tiger.” The last remnants existed perhaps as late as 13,000 years ago in California. Smilodon, though a fierce carnivore, is not related to any of today’s felines (“Felidae”) – neither the “big” cats nor your little finger-muncher. The disappearance of many such examples of Felidae might be due to failure to adapt to a changing environment, or possibly cross-breeding with incompatible species, producing sterile offspring. This happens today with crossbred lions, leopards, and tigers (producing generally sterile ligers, leopons, or tigons).⁷

Besides specific tooth types, the skeletal structure of a long, lithe body was an early evolutionary success, regardless of the animal’s environment. Some variants lived in forests and were semi-arboreal, where the ability to climb permitted a greater range of prey. Most members of the cat family retain that capacity, and the development of longer tails helped provide balance. Also, the very loose skin of Felis Catus evolved in a markedly different form than, say, the carapace of an armadillo, though both provide help in escaping predators. Manmade contemporaneous variants of the domestic cat, from the hirsute Persian to the hairless Sphynx, all retain the loose skin, paw pads with retractable claws, dentition of carnivores, flexible long back, and – with few exceptions – the long tail.

Today, some taxonomists divide the Felidae into three living subgroups of hunter-like carnivores, which differentiated as they adapted to varying environments: (1) Panthera – big cats capable of roaring, such as lions, tigers, jaguars, and leopards; (2) Acinonyx – Cheetahs, alone in this small subgroup because only Cheetahs lack retractable claws; and (3) Felis – the most recent to evolve but most variegated of the three subgroups, and the tribe which includes the kitten that chews on your shoelaces.

Spreading the Wealth

This differentiation began roughly 3-12 mya. Panthera were the oldest, dating from around 10-11 mya, followed by non-roaring large cats c. 6 mya, after which Felis appeared. The ancestors of today’s smaller cats then spread throughout the world, except in extremes of cold at the North and South Poles and bleak tundra areas that did not support prey. They developed individuation in size, coloration, and configuration of extremities, such as the Flat-headed Cat (webbed feet), the Sand Cat (strictly desert-dwelling, sand-colored), the Margay and the Rusty-Spotted Cat (both semi-arboreal), the Pallas Cat (thick grey fur concealing small size), and others like the Caracal, Oncilla, South African Wildcat, and Iberian Lynx: all with varying phenotypes. And, of course, the domestic cat, Felis Catus, our Fluffy.

Fossilized remains of cats have been found where humans lived back at least 7,000 years, but these were likely wild cats. Asian and North African species living closely with humans appeared in Egypt about 2000 years ago; the subsequent super-domestication of cats (e.g., deification) is recorded in some ancient Egyptian tombs. “[The] desert-living cat is now thought to have been the main ancestor of the domestic cats we have today.” The belief that domestic cats originated in such an environment is supported by anatomical features that provided a better chance of survival under desert conditions. For example, cats’ kidneys can concentrate urine much more than other domesticated species.⁷

Why Can’t Fluffy Roar?

An interesting anomaly in the throat is what eventually defined Panthera as a separate genus. The group, which includes lions, tigers, leopards and jaguars, has a different hyoid bone formation than other Felidae. Connected to the larynx, the hyoid in Panthera is partly cartilage, therefore flexible, permitting the roar. In the rest of the Felidae, the hyoid is hard, rigid bone.⁷ We cannot help but wonder why the larger cat developed this usefully intimidating trait while the smaller did not. Felis, however, can purr!

Mobility

Early mammals traveled the earth on variegated footwear, all gradually evolving into specialized functions of paws or hooves. The hooves of ungulate mammals (elephant, cow, horse, sheep) are like extra-large, tough toenails, enabling the animal to run on hard surfaces. Unguiculates (bears, coyotes, eagles, mice) are equipped instead with claws or talons. While soft paw pads are more vulnerable than hooves, claws permit grasping, climbing, and perching in a wooded environment. Just as hooves frequently branched into two or more toes, the paw pads had separate clawed toes. Felis Catus has five toes on each front paw, four on the rear paws. Some Felidae even developed retractable claws, a handy feline switchblade for hunting.

The Next Generation

Besides variations in teeth, feet, vocal apparatus, protective covering, and musculoskeletal development, these mammals could bear and suckle their young. When exactly the Miacids branched away from egg laying is unknown, but very few mammals today produce eggs outside the body. Eggs are a favorite prey of many species; the predominance of live birth carries risk as well, since newborn mammals require protection by adults of the species until they can stand, eat, run and perhaps hunt on their own. Big mom cats learned to look for caves, secluded rock formations and elevated places to ensure a safe place to give birth. Domestic cats have the same impulse, and homebody Felis Catus will explore open drawers and cupboards, dark closets, and out-of-the-way storage areas in a home to find a safe place for kittens.

And so the next generation of Fluffys will nurse. And grow. And engage in practice-fighting with siblings, to better ensure the strength and stamina required to catch the Wild Ping Pong Ball or Teaser Toy and drag it triumphantly back to his cave.

*While humans have 23 pairs of chromosomes (hence the company 23 and Me), cats have 19 pairs of chromosomes.

 

References:

1. https://www.geologypage.com/2014/04/paleogene-period.html
2. Strauss, Bob. The Evolution of the First Mammals, updated April 30, 2025 thoughtco.com/the-first-mammals-1093311
3. earth-site.co.uk/Education/cenozoic-era-66
4. Taylor, Christopher. “Creodonts”: Carnivores by Association, August 7, 2009 http://coo.fieldofscience.com/2009/08/creodonts-carnivores-by-association.html
5. Sole, F., Smith, R., Coillot, T., et al. Dental and Tarsal Anatomy of ‘Miacis’ Latouri and a Phylogenetic Analysis of the Earliest Carnivoraforms. Journal of Vertebrate Paleontology, Vol. 34, No. 1 (January 2014).
6. Polly, P. D. 1999. Creodonta. In: R. Springer (ed.), Encyclopedia of Paleontology. Fitzroy Dearborn Publishers, Chicago, pp. 316-317.
7. https://www.provet.co.uk/cats/evolution%20of%20the%20cat.htm