Within mammals, humans are one of the few species which cater to their taste preferences using spices. One of the spices used in cooking contains the active ingredient capsaicin which causes a burning or spicy sensation when eating. Of the mammals, humans and tree shrews are two of the few species who have been documented to consume plants containing capsicumoids as part of their diet (“Tree shrews can tolerate hot peppers,” 2018). Chili peppers are one of the most common cooking plants containing capsaicin, a type of capsaicinoid (Tsuchiya, 2001). Other mammals avoid the Capsicum plant species due to the spicy burning sensation caused by their consumption. Within tree shrews, they have a mutation on the reception TRPV1 which decreased the effects of capsaicin on the receptor (Han, Li, Yin, Xu, Ombati, Luo, & Lai, 2018). From this mutation, tree shrews were able to expand their diet due to their tolerance of capsicumoids in a similar pattern of convergent evolution. With humans, the burning sensation is variable depending on food preference of the individual but humans are the only species known to actively seek out the consumption of very spicy foods (Han et. al., 2018). TRPV1 receptors are apparent throughout mammals in their avoidance of spicy foods but only humans and tree shrews have evolved to utilize capsaicinoids in their diet. Of other vertebrates species, birds are one of the only other species to have no response to eating Capsicum plants (Han et. al., 2018). Birds are often used by plants to spread their seeds and it is likely that mammals do not do this job as well leading to the plant’s possible evolution to prevent their consumption by mammals.
"humans are one of the few species which cater to their taste preferences using spices" I just thought this sentence was a little awkward, but I enjoyed your paragraph. You covered a very interesting topic.
shortening wordy sentences
"Birds are often used by plants to spread their seeds and it is likely that mammals..." seems to be wordy. Consider shortening sentences to make them seem more confident, neutral, and factual. I would type something like: "...spread their seeds while mammals don't perform this role at the same efficiency."
This is a really interesting well-written paragraph. While it is really interesting that humans feel the burning sensation but still eat spices however, I don't think that this paragraph is about humans but rather about tree shrews. Because of this, it may be the best to leave that sentence out.