There is a brilliantly funny ad for Cravendale milk which was very successful, in which domestic cats rebelled against the human because he wouldn’t give them milk. All the rebellious cats had opposable thumbs and they behaved like humans. And that’s the point if you want to be serious about it. The cats became little humans and could do a lot more with their paws when they had those precious opposable thumbs. They could grasp hold of things. P.S. Cow’s milk is not good for cats as they are generally lactose intolerant.
Not that domestic cats need opposable thumbs to open doors because there are a lot of videos of cats opening fridge doors and interior doors so they can do pretty well without opposable thumbs 😸. But the thumb helps the hand grab hold of things. It’s a bit of anatomy which makes the hand more dexterous and handy.
Evolution
But there’s a serious evolutionary side to this amusing advert that we see on this page – seen by millions of people 😎. If cats had evolved to have opposable thumbs, they wouldn’t be cats. The cat’s paw with their sharp claws at the end of the toes is all about being a cat and doing feline things which basically means hunting prey; running fast and being very athletic. It means climbing beautifully. It means doing all the things that cats are so good at.
Not having opposable thumbs and being a cat go together. Being a digitigrade (walking on your toes) and having those elegant paws with paw pads and claws but no opposable thumb defines the cat.
Evolution is driven by the process of natural selection. Natural selection favours senses and anatomy which enhances an organism’s survival. The evolution of opposable thumbs for primates such as humans has been very useful for their survival but it was not something that was favoured in the evolution of cats. There are a few reasons for this:
Adaptive trade-offs: natural selection i.e. evolution involves trade-offs. I guess that means compromises. Certain characteristics are sometimes prioritised over others because of available resources and the environment. Cats are brilliantly efficient predators. The structure of their limbs and indeed their entire bodies including their sharp senses suit them very well for hunting, capturing prey and climbing as mentioned. If they had developed opposable thumbs, it would have required changes to their limbs structure, which would have benefited them in some ways but it would have been a negative in other ways. It seems that natural selection decided that the negatives outweighed the positives and so opposable thumbs did not evolve for felines. The negatives would have been that they wouldn’t have been able to hunt as they do. To run so quickly, to climb so athletically and so on.
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Niche specialisation: the opposable thumb gives the animal manual dexterity. In the way the cat evolved, they didn’t need that kind of manual dexterity. They rely on stealth, speed and agility. They rely on the ability to grab hold of prey with their claws and their forelimb strength. Because of the cat’s lifestyle of stalking and pouncing on prey, an ability to grasp and manipulate bits of a prey animal and other objects would not have been a substantial advantage to them over the negatives of having opposable thumbs.
Evolutionary history: my research indicates that primates have an evolutionary history of tree dwelling adaptations which favoured the development of grasping hands and opposable thumbs in order to manipulate objects. Think of primates swinging from branch to branch (a form of brachiation). The ancestors of modern cats diverged from the primate lineage millions of years ago. The evolutionary pressures acting on the cat lineage “favoured different adaptations for survival and reproduction”.
Evolution is based on randomly occurring genetic mutations which prove favourable to survival or the opposite. If it’s favourable then the mutation becomes a permanent fixture and if not, it fizzles away. There is no predetermined goal. It’s a bit haphazard and it takes millions of years.
Opposable thumbs for cats would have been useful in some respects but overall natural selection decided that they would have been a disadvantage to survival for the cat bearing in mind their lifestyle.
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