Your Inner Fish Chapter 3

Why do we all look different? Scientists try to solve these questions by looking into embryos and messed around with our DNA to see what would  change. Later they discovered the zone of polarizing activity (ZPA), something that instructs cells to produce different things, such as limbs. They named a gene Sonic hedgehog gene, one relating to flying and hypothesized that these genes are capable of making bodies look different. They found a supplier of shark eggs and started performing experiments on shark embryos since they are very distant from humans. And the results matched with the chicken experiments. That was how scientists solved the answer to what makes us look different