Human beings are somewhat unusual among primates in the length of their life span beyond their productive years. this may have provided an adaptive advantage over the course of evolution and is known as

Human beings are somewhat unusual among primates in the length of their life span beyond their productive years. This may have provided an adaptive advantage over the course of evolution and is known as grandmother effect. This effect occurs when a grandmother takes care of children beyond her menopausal age, around 40 to 50 years old and is able to outlive the production years of her life. It provided the grandmother a chance to live more by taking care of her grandchildren to free her children from other tasks. It is an evolutionary phase for the woman who are past their menopausal change aside from the long term marriage from their partners. That is why, grandmothers tend to live more years compared to grandfathers.

By water evaporation from the leaves is created a negative pressure at the top of the tree that promotes the ascension  of the water through channels that are called xylem. there are also two molecule forces that are involved: the intra-water molecules cohesion (water molecules stick to each other) and the adhesion when the water molecules stick to the channels they are running in. this is what enables water to go from the roots to the top of a tall tree.