One of Charles Darwin's predictions was that evolution occurs gradually via variations within populations. His friend Thomas H. Huxley was concerned that Darwin had assumed "an unnecessary difficulty in adopting Natura non facit saltum [nature does not make leaps] so unreservedly." But Darwin's theory would have been much less compelling without it. Imagine if evolution had included the caveat that saltations—rapid leaps—can occur by unknown mechanisms such that new fossil species can appear fully formed. This would have destroyed Darwin's premise that species evolve by natural processes and we wouldn’t be talking about him today. Yes the fossil record suggested that nature does take jumps, but it was safer for Darwin to question the data than to admit them into his theory.
In order for evolution to succeed Darwin would need to steer clear of the supernatural, or anything that could be interpreted as supernatural, and argue for a strictly naturalistic origin of species. Darwin could hardly argue for a naturalistic origin, and then propose a theory that suggested a supernatural interpretation.
In its first century evolution maintained Darwin's hope that the fossil record was incomplete. Aside from a few heretics such as Richard Goldschmidt and his hopeful monsters, most evolutionists carefully avoided the problem of stasis and abruptness in the fossil record. But scientific evidence doesn’t go away.
Today the specter of saltational evolution persists, and probably is here to stay. In recent years evolutionary studies have increasingly appealed to saltational evolution to explain a variety of biology’s wonders. For the angiosperm flower to Cirripedes (a Darwin favorite) and the turtle, evolutionists are saying saltational evolution should be considered in addition to the many other explanatory mechanisms.
Of course the appeal to hopeful monsters is certainly not evolution’s first or only use of one-time or strange events. From history changing endosymbiosis events to meteorite impacts, evolution is the story of contingencies. So why not a saltational event now and then? As evolutionist Ernst Mayr wrote, "Laws and experiments are inappropriate techniques" for explaining evolutionary events and processes. Anything can happen in this theory.