increased vs greater - "only suggest greater diversity today, while in actuality"

Question

this is a sentence from GRE:

Some paleontologists debate whether the diversity of species has increased since the Cambrian period, or whether imperfections in the fossil record only suggest greater diversity today, while in actuality there has been either stasis or decreased diversity.

I don't exactly understand the latter part of the sentence: specifically, (1) what does "only suggest" mean here? I took it to mean that "the imperfection perhaps purely suggests a more diverse world today." But under this understanding, the second whether would be redundant with the first whether, because both would be talking about the diversity is increasing. Thus, I was very confused when I interpreted it this way. After checking dictionaries and public resources, I still couldn't figure out how to make sense of the sentence.

(2) I have huge trouble in understanding what this part is saying: "Or whether imperfections in the fossil record only suggest greater diversity today, while in actuality there has been either stasis or decreased diversity." If a greater species diversity is suggested, then how come such a greater number could possibly be turned out to be a stasis or decreased diversity?

Any sharing would be greatly appreciated.

Answer 1

"Only suggest" means that the evidence sort of points in that direction, but is far from definitive. If this is correct, then a lot of further investigation would be needed. "Only suggests" is pretty mild evidence.

The whole sentence says, basically, that the suggestion is incorrect.

As an analogy, imagine that there has been a theft. Bob is a suspect. Then you could say "The fact that Bob was in the store 5 minutes before the theft took place only suggests that he stole the goods, while, in actuality, the video of Carol taking items from the shelf and putting them in her bag before walking out shows that Bob is innocent".

Answer 2

The writer is describing two opposing groups of paleontologists: those who believe that diversity has increased, and those who believe it has decreased or stayed the same.

The latter part of the sentence is explaining the views of the second group. By "only suggest" the writer seems to be saying something like:

or whether imperfections in the fossil record falsely imply greater diversity today

They are saying that some paleontologists believe that the imperfections may be deceiving and lead us to incorrect conclusions. A suggestion is not as strong as an assertion. And if someone gives "only" a suggestion, they are not asserting their opinion as 100% truth.

Therefore, the second group of scientists think that a superficial examination of the fossil record may only provide suggestions, not definitive truths.

The next phrase:

while in actuality there has been either stasis or decreased diversity

suggests an alternative explanation to the false implication.