Why do cats and tigers look so similar?

Regarding cats and tigers, many people have probably noticed that these two completely different animals look quite similar except for their body shape. What is the reason for this and why is there such a strange phenomenon?

In fact, the reason why cats are so similar is mainly because of the short evolution time and the speed of diffusion. Today I will talk to you about this issue from the perspective of evolution. Welcome to watch!

01. Let’s talk about the issue of evolution

Let's talk about evolution first. I guess you have seen a lot of pictures like the following.

Of course, there are more subtle pictures.

However, this graph is not defined arbitrarily by humans, but is calculated based on genes, which is often called the molecular clock.

The number of substitutions of a certain protein between different species is nearly linearly related to the divergence time between the species studied, and this constant-rate variation at the molecular level is called the "molecular clock."

This calculation includes both genes and fossil evidence, and finally some molecular clocks are calculated (of course there is a fluctuation up and down).

This is why we can calculate the evolutionary time of an animal by examining its genes.

The closer the evolutionary distance, the higher the genetic similarity, and naturally the more alike they are. If you don't understand, you can think about how the paternity index (STR) in paternity testing comes from.

Cats are genetically clustered, which is why cats and tigers are very similar.

02. The reason why cats and tigers are similar

Then someone asked, why do cats and tigers show clustering in genes? There are two main reasons, please see below.

1. Separation time is too short

The time from the ancestor of cats to the emergence of cats is not particularly long, although the ancestor was 18 million years ago, while most cats may be millions of years old, for example, lions/tigers/leopards appeared about 3 million years ago. 3 million years seems like a long time, but in terms of evolution, it is basically not worth mentioning, and even most cats are on the scale of 1 million years.

Because the basic unit of evolution is millions of years (M), the difference between two species can easily be hundreds of millions of years. The short evolutionary time determines that the variation of traits will not be particularly large.

2. Rapid diffusion

This question is mainly about reproductive isolation. An important link in reproductive isolation is geographical isolation, such as the Qinling giant panda and the Sichuan giant panda are geographically isolated.

The rapid spread of cats also led to frequent genetic exchanges among them. For example, tigers and lions can still exchange genes today.

03. Why do the rules of human resemblance not apply to cats?

Perhaps, some netizens will raise the question again. In our human race, only close relatives look alike, but cats and tigers are two completely different animals. Why don’t human evolutionary rules apply to cats? In fact, friends who raise this question may have fallen into a logical circle. Why are the two children so similar? It’s really because they have the same parents. The deeper reason behind it is the consistency of the genetic source or the high similarity of genes. Similarly, although the cat family is defined by humans, cats are genetically clustered together, so they look alike.

Just like the reason why you and fish are not alike is because the evolutionary distance between you and fish is too far, and this evolutionary distance is essentially because your genetic variation is too great. Genes determine traits, and naturally the traits are also very different.

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Of course, cats and tigers belong to different genera, so there are still significant differences. For example, the typical difference is huge in body size. However, for the genus Panthera, to which tigers belong, the body sizes are basically the same.