I agree completely-that was the original plan. But the plan had to modified when our ancestors decided to run amuck and completely turn their back on God. When God decided that they had gone as far as He could let them without them destrying the earth, He decided to limit mans ability to influence succeeding generations.
See, the earth before the flood was a wonderland. We were designed to live forever, and until our first parents screwed that up, we did. But after they were denied access to the tree of life they lost their immortality. But the earth was still a paradise. A person could get all the nourishment he or she needed buy walking to the nearest fruit tree and picking something off of it. And the variety was astounding. The atmosphere was different, which contributed to lifespans of around 600-900 years.
Part of the deal with the flood was the disruption of most of the factors that led to long lifespans, because God knew that if you let people live more than a couple hundred years that they have a tendency to get themselves into trouble and that had to be addressed. One of the things He did was to give Noah meat to eat. But it was specific meat. Not everything was supposed to be consumed by man. In fact, this was so important that after this truth was lost by the isrealites while they were slaves in Egypt, God had to have it written out for them by Moses so there wouldnt be any questions.
But aside from shortening lifespans, it was also the fact that Noah and his family were basically stranded in a desolate wilderness and needed sustenance at least until they could plant a garden and harvest it . I bet it was a tough first year for people that had never eaten meat to get used to it-not to mention that they had personally taken care of those animals on the ark for a year or so and were probably pets.
