The scientific theory says that the life around us could have arisen by processes which have no goal. By no goal, I mean that the processes are not aimed to a particular end, and have no preferred outcome.
In particular, these processes do not in general try for "higher" life forms, or for larger ones, or for more complicated ones. Those can happen, of course. But there are also creatures which are smaller and simpler than their ancestors. This can be seen in the fossil record. It can be seen today in parasites which have lost some of the features of closely related species.
There are also processes which do have a direction. For example, a creature which is a slightly better mimic, or has a slightly better eye, would be favored by natural selection. The peacock's tail is so large because a selection process (sexual selection) had a direction. To peahens, bigger was better.
Scientists who are religious don't see a conflict between the statement above, and their personal beliefs. God may have interfered with the events of the natural world. But, He did not shape the natural world so as to be dominated by processes having a direction.