They probably lived in East African grasslands $2$ million years ago $(MYA)$. Who are they?

Trace the various components of human evolution (hint: brain size and function,skeletal structure,dietary preference,etc.).

What was the most significant trend in the evolution of modern man ($Homo$ $sapiens$) from his ancestors?

The first mammals were like $A$. Their fossils are small-sized. Mammals were $B$ and protected their unborn young inside the mother's body. Choose the correct option for $A$ and $B$ to complete the given $NCERT$ statement.

$A$: Evolution of shelled eggs helped the reptiles to successfully adapt for terrestrial life.
$R$: The origin of shelled eggs occurred earlier than viviparity.

Currently,the $DNA$ sequence of $mtDNA$ and the $Y$-chromosome are considered for the study of human evolution because: