"The right-handed twin accused his brother
of murdering their mother, and their quarrels
continued until it was time to bury their
mother. With the help of their grandmother,
they made her a grave. From her head grew
the three sister plants: corn, beans, and
squash. From her heart grew tobacco, which
people still use to give thanks in ceremony.
She is called 'our mother' and the people
dance and sing to her to make the plants
grow.”
The myth attempts to explain

what does the myth attempt to explain ?