I have always wondered how from Adam and Eve came all the different races and colors of the peoples of the world? Was it like that from the start? If not, how did the variations occur?
Great question! The Talmud itself deals with this. In reality, the modern concept of adaptation to the environment is discussed in the Talmud written 1800 years before Darwin was born!
The Sages thus taught that in order to help people survive in different climates and conditions, G‑d created them with the ability to adapt physical characteristics specifically suited for their environment. For example, the Talmud states (Shabbat 31a) that for this reason people who live in swampy regions may have large feet to help them contend with the soft ground. And those who live in desert climates developed specially shaped eyes which help them contend with the sand that is prevalent in the air.
In the same line of reasoning, we can clearly postulate that G‑d created mankind with melanin which would adjust the epidermis of people who live in different longitudes in a way that would help them to contend with the varied exposure to the angles of the sun’s rays.
This is clearly the way G‑d created the whole world. Many times in Tanach we see that G‑d created everything with wisdom and benevolence, imparting in everything the innate ability to survive and contend with its environment. Not only does G‑d give all life its capability to survive, but He also created the inanimate world in its many manifestations in a way that protect and enhances that life. “How great are Your works, O Lord! You have made them all with wisdom; the earth is full of Your possessions!” (Ps. 104:24).
For example, King David wrote that G‑d gives “snow like wool” (Ps. 147:16) What kind of comparison is this? Snow is cold and wool is used to warm and protect? Yet, careful observation gives us the answer: Snow acts like an insulation to protect the ground and its vegetation from the extreme cold of winter. The more toward the poles we traverse the more snow there is, further insulating the ground underneath. Many animals, seeking warmth, actually burrow themselves in the snow during extreme temperatures.
In his inspired wisdom, King David perceived this concept of ground insulation marvelously. Differences among people, too, can be seen as helpful adaptations from a benevolent Creator.