Neurons exposed to chimpanzee ApoE ACM developed shorter neurites and reduced spine density than ApoE3, confirming prior studies on the restrictive influence of ApoE4 on neurite outgrowth and synaptic maturation.33,34 Unique to chimpanzee ApoE was the increased number of neurites per neuron, suggesting a divergent influence on early neurogenesis that may reflect adaptive evolutionary traits unrelated to AD vulnerability. Here, APOE is linked to Alzheimer disease.