Modern-day snakes are believed to evolve from four-legged

[asker]

Modern-day snakes are believed to evolve from four-legged lizards, but scientists were divided over whether that phase of evolution occurred on land or in the sea; the recent discovery of fossils of a land-dwelling snake with two legs provides new information for the ongoing debate.


a evolve from four-legged lizards, but scientists were

b have evolved from four-legged lizards, but scientists are

c evolve from four-legged lizards, but scientists are

d have evolved from four-legged lizards, but scientists were

e be evolving from four-legged lizards, but scientists were

Explanation:
There are two verb tense errors in the original sentence. First, the present tense “evolve” indicates that snakes currently change from four-legged lizards into serpents. It is more accurate to use the present perfect “have evolved” to indicate that the evolution started in the past (beginning with the four-legged lizards of the past) and has continued into the present (resulting in the snakes of today). Second, scientists are presently divided over the land-versus-sea evolution debate (“…the ongoing debate”), so the past tense “were divided” is not correct.



I was right for the second tense, scientists are is in the present tense without issues. My question is why the first verb, evolve, should use present perfect. I have several from OG, similar historical problems, all wrong in present/past perfect tense.

EG1: OG13-128: "trunk originally evolved" (sorry not allow to post official question, so just several key words here)
EG2: OG13-7: "it evolved independently"

Although I can understand this:
OG13-76:"appear to have been equipped", Neanderthals no longer exist, so use perfect tense.

Here snake still exist in the world, and the evolution can be treated as a eternal fact, so I think simple present tense is right.

Please correct me where I'm wrong in this analysis.