Am I missing any important punctuation in this sentence:

Scientists and doctors alike have only come up with one sound conclusion to date: based on what they’ve seen yet, the Ram is a creature which will no doubt affect the environment it lives in greatly, and it will not be easily extinct.

I feel like there is a semicolon or a comma missing.

Thank you and Happy Thanksgiving!

I see no punctuation errors, but the B on "based" needs to be capitalized since it's the first word in a sentence following a colon.

http://grammar.ccc.commnet.edu/grammar/marks/colon.htm

http://englishplus.com/grammar/00000044.htm

Also the word "only" needs to be moved closer to what it modifies; it should be between "with" and "one." And the adverb "greatly" is awkwardly placed; it would be somewhat smoother if it were between "no doubt" and "affect."

I'd also delete the word "yet" since the phrase "to date" is in the previous clause.

=)

In the given sentence, there is no requirement for a semicolon or comma to be added. The sentence is grammatically correct as it is. However, if you want to improve the clarity and flow, there are a few alternative options to consider:

1. Use a colon instead of a comma after "conclusion to date":
Scientists and doctors alike have only come up with one sound conclusion to date: based on what they’ve seen yet, the Ram is a creature which will no doubt affect the environment it lives in greatly, and it will not be easily extinct.

2. Split the sentence into two for better readability:
Scientists and doctors alike have only come up with one sound conclusion to date. Based on what they’ve seen yet, the Ram is a creature which will no doubt affect the environment it lives in greatly, and it will not be easily extinct.

Remember that punctuation helps convey meaning and structure, so it's always a good idea to review your sentence for clarity and coherence. Happy Thanksgiving to you too!