Mammals are a class of animals that includes human beings, apes, monkeys, elephants, mice, and many other creatures. All mammals have some hair on their bodies, but not all mammals have eyelashes. So the answer to the question is no, not all mammals have eyelashes.
There are two main types of hair found on mammalian skin: primary hairs and secondary hairs. Primary hairs are the long thick hairs that grow on the head and coat the body. Secondary hairs are much thinner than primary hairs and often barely visible to the naked eye. Eyelashes are classified as secondary hairs because they are much thinner than primary hairs.
The function of eyelashes is to protect the eye from debris, dust, and other foreign particles that could potentially damage the eye. They also help to keep moisture in the eyes by providing a seal against wind and dry air. Additionally, eyelashes play a role in human communication by accenting facial expressions.
While all mammals have some form of hair on their bodies, not all mammals have eyelashes. This is because lashes are classified as secondary hairs, which are much thinner than primary hairs. The function of lashes is to protect the eyes from debris and dust; they also help keep moisture in by sealing out wind and dry air. Additionally, lashes accentuate facial expressions in humans and other animals communicating non-verbally.