Question: Daniel asked an interesting question - “I’m confused, were not the Sumerians, like everyone else, supposed to have descended from Noah?”
Answer: A quick look around the world will show us that we did not all descend from Noah and his three sons Shem, Ham and Japhheth. And that is before we begin to enquire about the excellent advances that have been made in genetics, archaeology and paleontology that inform us about our predecessors' history.
Our ability to sequence DNA has increased dramatically since the human genome was first sequenced. When living cells die their DNA doesn’t immediately disappear, meaning that the DNA of ancient dead people can still be found. So we know far more than previous generations about the genetic history of human beings.
We also find that Genesis agrees with modern discoveries about our genetic history.
After the Flood the Sumerian speaking people again came “from the east,” as the King James Version puts it, (Gen 11:2). So, if they came from the east they did not descend from Noah. There were some Semitic people who had obviously descended from Noah, i.e. Terah and his family that included Abraham. Terah’s family travelled from the west and ended up in the south-eastern Mesopotamian city of Ur.
We can quickly look at why the Flood was the reason that people thought modern humanity emerged from Noah, if it’s helpful.
There was more than one reason for the Flood. Adam’s clan was getting out of hand, God said he was sorry he’d even put man (Adam's family) on the earth. Something had to be done and the Flood was the answer. The Flood was mainly to free the earth of Adam's descendants, because they had gone seriously bad. Every thought and inclination of their hearts was evil all the time. Secondly, the hybrid Nephilim could also be largely destroyed, but not all of them would be wiped out as Genesis 6:4 explains that some of them were around after the Flood too. But God sent the Israelites (among others) to track them down and one of the last of them to go was named Goliath who was killed by a boy named David.
Some people used to talk about a global flood, (and some probably still do) but this is another addition to what we have in the Bible, the word “global” isn’t there, neither is “worldwide” or “universal.” Some English translations of Genesis 7:20 tell us the mountains were covered to over 20 feet (15 cubits), the Septuagint helps us understand that the waters were 22 feet high from the ground and because Mesopotamia is a largely flat landscape, any hills there were also covered. The KJV agrees, “Fifteen cubits upward did the waters prevail; and the mountains were covered.” The word for mountain in Hebrew is the same as hill or hill country. The Tigris-Euphrates basin is extremely flat, and the area is an alluvial plain, which means periodic floods have always occurred every now and again. In spring the snows in the Turkish mountains would melt and the levels of the two rivers, Euphrates and Tigris, would be raised, and some years the rivers would break their banks because the area is so flat. There would be natural levees around where villages, towns, and cities could be built; they would be on slightly higher ground. The cities had to be built on the turtle-back levees because the flood plains would be swampy for some time after a flood. Most hills in this region that are as much as 15 meters high are more than 95 km away from the river levees. Therefore, when Noah looked out of the one cubit gap between the upper deck and roof he would see only water in all directions. “and the waters prevailed exceedingly upon the earth; and all the high hills, that were under the whole heaven, were covered” (Gen 7:19) - as Noah looked at the horizon, 360 degrees of it (“the whole heaven”), the land was entirely covered in water. Noah would have measured the depth of the waters, he was a builder, craftsman, and an excellent engineer, so measuring the depth of the waters as the ark floated upon them was something he would want to know and something he was capable of finding out. He concluded the depth to be 22 feet.
“Every living thing on the face of the earth was wiped out” (Gen 7:23). Genesis talking about the "face of the earth" being covered with water, probably made some people think that what we modern people mean by "face of the earth" was the same as what people meant in the ancient world. But what we mean by it and what they meant by it are different. The “face of the earth” is the same phrase that Cain used when he said he was being driven from the “face of the earth.” When Cain said, “face of the earth” he didn’t mean the whole earth just the area of land he was on at that time, the part of the earth whose face he could see. Noah too.