Natural toxin implies bitter taste.
This section will focus on proposition B. Lack of proof for the claim that bitter implies toxic. For the bitter rejection response to be an effective poison detector, there should be a predictable relationship between the threshold concentration for bitterness and that for toxicity. If the bitter threshold is substantially higher or lower than the toxicity threshold for many compounds, the effectiveness of the bitter rejection response as a poison detector would be uncertain. To the author's knowledge, no investigator has explicitly tested for such a relationship across a series of bitter compounds. The bitter taste threshold in mice varies according to the autosomal gene Soa.