According to evolutionary theorists, the smile and appearance of a baby causes adults to become attracted to the baby and increases the willingness of parents, grandparents, and other possible caregivers to go from busy adults to devoted caregivers. evolutionary theorists believe that this occurs in adults because of:

Evolutionary theorists believe that this occurs in adults because of an evolutionary response that will ensure the survival of the baby. You have to remember that babies are borne helpless, they need care and protection from caregivers and there are many factors that can trigger a protective response in parents such as a smile, a giggle, smell, cry, and facial gestures that capture the parents attention.

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unicellular organisms, like bacteria, are able to perform all life functions within one single cell. multicellular organisms need many different types of cells to carry out the same life processes. each of these special types of cells has a different structure that it perform a specific function.