Why can the adverb "otherwise" be used followed by a verb as an object in the sentence "But the research suggests otherwise"?

Question

In the sentence

But the research suggests otherwise,

we know "suggest" is a transitive verb, so my question is, what "otherwise" is then? I guess it's an adverb here, but we must use suggest + noun/v-ing or that clause as an object right?

If "otherwise" here is used as an adverb, does that means "suggest" can be used as an intransitive verb? Or an adverb can be used as an object? I don't think so, thus I'm really confused.

If "otherwise" here is not used as an adverb here, then what is the component of "suggest" in the sentence?

The complete sentence is:

‘It might be what we find interesting about this story is that it’s got this survival-relevant information in it,’ says anthropologist Jamie Tehrani at Durham University in the UK. But his research suggests otherwise. ‘We have this huge gap in our knowledge about the history and prehistory of storytelling, despite the fact that we know this genre is an incredibly ancient one,’ he says.

Answer 1

Under Adverb Collins gives this definition of otherwise

You use otherwise to refer in a general way to actions or situations that are very different from, or the opposite to, your main statement.
[written]

• Take approximately 60mg up to four times a day, unless advised otherwise by a doctor.
• I wanted this to be my wedding song, but was convinced otherwise.

It is used as an adverb. You can replace it by differently or in a different way. The direct objects of the verbs advised, convinced or suggested are implied. They will be something different or opposite from what was mentioned before.

It is true that the direct object must be expressed in a sentence with a transitive verb, except when it is so obvious, that it will be understood even if it is absent. In some cases, the sentence will be more successful if it is left unsaid, as it avoids unnecessary repetition. An example of this would be what Thought.co quotes from Gail Brenner, Webster's New World American Idioms Handbook. Wiley, 2003:

Some transitive phrasal verbs do not use their direct object when the direct object is implied in the meaning of the idiom. For example, with the phrasal verb pull over (to move a vehicle out of the flow of traffic, and slow down or stop), it's not necessary to say

I pulled the car over

because the car is implied by the idiom. You can simply say

I pulled over.

In your case, let's say that someone says A, but the research suggests B, C, D etc. which are different from A. This is expressed by the adverb otherwise. You can read this statement as:

But his research suggests otherwise [that...].

The sentence following, expresses what his research suggests.