Evolution or Manifestation

The interesting case of the spider tailed horned viper.

https://www.youtube.com/shorts/MkYluH1BtvU

The above video made me question the Darwinian theory of evolution.

Among all the snakes, how did this grow such an animal looking tail? Doesn't look like an evolution from anything near by.

I asked ChatGPT to explain the evolution of the spider tailed horned viper.

Its response:

Evolution does not “plan” spiders. It selects incremental advantages.

Stage 1 — Slightly Modified Tail Scales

Random mutations cause:

• Slight enlargement of tail tip scales

• Irregular keratin projections

If these movements vaguely resembled insects, birds may have approached more often.

Even a 5–10% hunting advantage → strong selection pressure.

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Stage 2 — Selection for Leg-like Projections

Over generations:

• Mutations producing elongated, movable scale extensions

• Enhanced muscular control of tail tip

Birds (especially insectivorous passerines) mistake the motion for arthropods.

Snakes that looked “more spider-like” ate more.

They reproduced more.

Trait frequency increased.

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Stage 3 — Fine-Tuned Mimicry

Eventually:

• Tail morphology became highly specialized

• Behavior evolved alongside structure

• Neural circuits adapted for rhythmic, spider-like twitching

This is co-evolution of morphology + behavior.

What I am not able to digest / understand is this: The mutation might have occurred with 1 viper. And it somehow became a dominant gene and that snake mated with so many other snakes that it managed to create a species eventually? 
Sounds more like Genghis Khan. 8% of Asian men have ancestry of Genghis Khan.

Or did the viper manifest a spider like tail and got it?