No, in the days before the flood, people lived much longer. Methuselah lived the longest of any person.
The explanation which always satisfied me is the following. Adam and Eve were created to live forever, in perfect conditions. But when they sinned, death entered the world, although not immediately. Adam finally died when he was 930 years old, in Genesis 5. Many of the ancients before the flood lived for centuries, read Genesis 5 to see the people and their ages. Longevity was the rule, not the exception!
So in chapter 6 of Genesis, God becomes angry with human beings for various reasons. He picked Noah, a righteous man to build the ark. It was not just a flood from the sky, but also the "waters of the deep" Gen. 7:11, opened up. So this was a BIG flood. Plus, if there had been a protective canopy over the earth, as some postulate, by dumping that canopy on the earth, all people, plants and animals were open to the excessive radiation from the sun, and the mutations caused by it. I think other things also entered the environments of people, as the first mention of alcohol is after the flood. Perhaps the yeast needed to make alcohol came from the rain or the juvenile water??
So you have totally new conditions in the earth. A these conditions accelerated, people began to suffer more and more under a genetic load - that is mutations which favoured diseases and resulted in shorter living times. This continued up to the time of Abraham, who died at the "ripe old age" of 175 years (Genesis 25:7), Isaac who lived 180 years (Gen. 35:28), Jacob who lived 147 years (Gen. 47:28), his son Joseph at 110. (Gen. 50:26)
There is a real downward trend from Adam and Methuselah to the end of Genesis, after the flood in length of life. Moses is recorded to have died at age 120 in Deut. 34:7. So things level off. Yet as we know today, the person who lives to 120 is the exception to the rule, not the rule.
I also believe God's prohibition to the Jews against marrying sisters and cousins, which begins in Lev. 18:6-18, is because of the genetic load which narrowed the genome considerably, especially considering Abraham married his half sister, and his sons also married relatives from Haran. In fact, this prohibition continues today, because of the possibility of interbreeding producing bad mutations. I once worked teaching handicapped students, and there was a family whose parents were cousins. Four out of the five children had facial deformities and were mentally handicapped, as a recessive trait was expressed in the children.
So the perfection created in Eden, allowed those early inhabitants of the earth to live much longer than we live today, and Methuselah lived the longest of them all.