Phenotypic Feature (Examples)	Human Lineage Specific Trait	Possible Evolutionary Advantages
Brain growth trajectory	Prolonged postnatal brain growth and delayed myelinization period; Enhanced cognition	Allowed creation of novel solutions to survival threats, increased the critical period of learning new skills, and facilitated emergence of uniquely human cognitive skills
Brain size	Increased brain-body size ratio; Enhanced cognition	Allowed creation of novel solutions to survival threats and improved social cognition.
Descended Larynx	Portion of tongue resides in throat at level of pharynx. Larynx descended into throat	Helped enable spoken language
Eccrine sweat gland density	Higher density of eccrine glands; enhanced sweating capacity	Enhanced cooling ability; protection of heat-sensitive tissues (e.g. brain) against thermal stress. Facilitated endurance running.
Endurance running	Improved energy utilization during periods of high energy demand; Increased capacity to transfer energy (glycerol) from fat stores to muscle; Anatomical changes relating to running ability	Allowed persistence hunting to emerge as a viable strategy for accessing the benefits of increased meat consumption Increased range of food sources Improved diet may have facilitated brain evolution
Labor	Earlier onset and longer duration of labor	Partially protected child/mother from damage due to increased head circumference
Lacrimation	Emotional lacrimation (Crying)	Enhance emotional communication within social groups Increased affective communication
T cell function	Relative T cell hyperreactivity	Enhanced immune function
Thumb	Increased length, more distally placed, larger associated muscles	Created more detailed tools Manipulated objects on finer scale