Yes they were. However how do we know or even suspect that this is true? Let’s begin the beginning when God created Adam and Eve. He fashioned them in His likeness and image. They were tall, good-looking and extremely intelligent with the capacity to live forever.
The world at that time was nutrient rich and lush (which is why we have such enormous coal beds – formed from the lush, huge plant life before the flood). It was perfect and people were perfect so to speak. After the fall of man, humans began to degenerate in size, intellect and lifespan. This is why we find in the the fossil record giant plants and animals. Lifespan before the flood, the Bible says, was 900+ years. If life on earth was generally larger in size (dragonflies with 29” wingspans) then why could there not be giant humans?
Unfortunately today, plants and animals are much smaller and the average height of a man is 5’10” and woman 5’4″. Instead of living a millennium we live to be on average 75-85 years with the upper end of 120.
Therefore, the Nephilim or giants mentioned in Genesis 6 and in several places in the old testament were simply the offspring of our giant parents, Adam and Eve.
Do you want to explore this topic further? A must read is Jon Gray’s book Lost World of Giants and you can grab a copy in our museum’s store.