How do scientists know that humans originated in africa?

Where do homologous chromosomes exchange genetic material through crossing over?               a.  chlorophyll    b.  centrosomes    c.  centromeres    d.  chiasma

Explain the source of radioactivity in uranium in earth’s crust by which it produces nuclear radiation

The mammal pictured below is a silvery mole rat. which statement is an inference based on the picture? the animal is ugly. the animal has hairless feet with sharp claws. the animal has prominent upper and lower incisor teeth. the animal likely has poor vision since its eyes are so small.