[tomerico]

Interesting watch. TL;DW - Apes like Koko were raised by trainers who did not perform rigorous scientific measurements and were prone to bias. Research on Apes became immoral over time, hence less recent examples exist.

The most recent and rigorous study is on a bonobo, where communication is done using touchscreen with buttons saying words (lexigrams). Even in this case interaction seems to be limited to “give me an item” or “put item in box”.

[barrkel]

Do you mean fewer recent examples exist?

"Less recent examples exist" is a positive assertion about the existence of even older examples. The 'less' attaches to the 'recent'. 'Less' can't attach to 'examples' because you can't have 'less examples', because 'examples' is countable.

"Fewer recent examples exist" is a negative assertion about the existence of newer examples. The 'fewer' attaches to the 'examples'.

[TulliusCicero]

> Research on Apes became immoral over time

Teaching apes sign language became viewed as immoral?

[ReaLNero]

Raising them only by interacting with a single person (not of their species!) would be immoral for a human baby, and depending on your views of ethics, also immoral for a gorilla.