New channels open where there were once sandbars and shoals. What is happening in our time is more like a hurricane than an accumulation of smaller storms. Our time is a pivotal one in the history of mankind. If the Lord tarries, these years will be seen as a time when the entire world changed direction - for good or for ill. Unlike many non-Christian world views, Christianity does not see history as a series of cycles.
History certainly does repeat itself in various ways, and yet, history always moves forward.
Today is never exactly like the past. There are situations, problems, and opportunities today that never existed before. Previous societies could do selective breeding, for example, but no previous generation has had to deal with the morality of genetic engineering. This does not mean that previous generations did not have to face some very large and critical issues. It does mean that they didn't face issues such as this one in the past, or at least not in the same way and under the same circumstances.