In Gen ch 1 because we do not read about Adam until Gen 2. 1:27 So God created man in his own image, in the image of God created he him; male and female created he them.
In Gen 2:4 we read: "These are the generations" Then in Gen 5:1 "This is the book of the generations of Adam." So the generations are made very clear in the Bible, just exactly who is decended from Adam. The DNA confirms what the Bible tells us.
Abraham's Chromosomes?
2:23 And Adam said, This is now bone of my bones, and flesh of my flesh: she shall be called Woman, because she was taken out of Man.
2:24
Therefore shall a man leave his father and his mother, and shall cleave unto his wife:
I am sure you have a different understanding. But clearly we are told here that Adam has a mother and a father. That he was to leave his mother and father and cleave onto his wife.
We now have a man and a women, a husband and a wife for the first time. Before we only had a male and a female. As the country music people love to talk about how there is a difference between a male and a man. A female and a women.
Then we see: Genesis 3:20 "And Adam called his wife's name Eve; because she was the mother of all living." What does this mean "all living"? This is the sixth time we see this word "living" in the Bible. The word "all" is not in the original Hebrew, the translaters added the word "all" in this passage.
4:14 Behold, thou hast driven me out this day from the face of the earth; and from thy face shall I be hid; and I shall be a fugitive and a vagabond in the earth; and it shall come to pass, that every one that findeth me shall slay me.
Just who was it that Cain was worried about killing him if there were not other people alive on the earth at that time?
4:16 And Cain went out from the presence of the LORD, and dwelt in the land of Nod, on the east of Eden.
4:17 And Cain knew his wife; and she conceived, and bare Enoch: and he builded a city, and called the name of the city, after the name of his son, Enoch.
We are told that Cain went to the land of Nod and there he found a wife. He built a city. A married man does not build a city unless there are people to live in the city.
So these are the main scriptures that talk about people in the earth before Adam and Eve. But there is also the story where Jesus called the people who were not of the House of Israel: "DOGS". These are the people who are not a part of the generations or the descendants of Adam and Eve.
21Then Jesus went from there, and departed into the regions of Tyre and Sidon.
22And, behold, a woman of Canaan came out of the same regions, and cried unto him, saying, Have mercy on me, O Lord, you son of David; my daughter is grievously vexed with a demon.
23But he answered her not a word. And his disciples came and besought him, saying, Send her away; for she cries after us.
24But he answered and said,
I am not sent but unto the lost sheep of the house of Israel.
25Then came she and worshiped him, saying, Lord, help me.
26But he answered and said,
It is not right to take the children's bread, and cast it to dogs.
27And she said, True, Lord: yet the dogs eat of the crumbs which fall from their masters' table.
28Then Jesus answered and said unto her, O woman, great is your faith: be it unto you even as you will. And her daughter was made whole from that very hour.
If you remember we are adopted into the family of God. We are not a natural branch of the tree. The Hebrews and the Arabs are the natural children of Abraham.