All histories are part of the humanities, which are separate from the sciences. There is no scientific history or historical science – that would be like a round square.
A purported scientific history or historical science is either science and not history or history and not science. A scientist who writes histories is to that extent an historian, not a scientist.
Histories are focused on significant dissimilarities, discontinuities, and particulars. Sciences are focused on significant similarities, continuities, and universals.
Histories are diachronic or diatopic; that is, they are about a sequence of events through time or through space. A history takes a particular place or subject and follows them through a time line; or it takes a particular subject and follows them through a baseline, as with a journey. Histories are written as narratives.
Sciences are synchronic or syntopic; that is, they are about a particular time or place or object. A science takes a particular period or object and explores it in 3D space; or it takes a particular place and explores it in 3D time, as with a field trip. Sciences are written as theories.
Science can emulate history to a limited extent by dividing time into periods, each of which is approached synchronically. However, the periods must be discontinuous and exclude anachronistic chronology.
History can emulate science to a limited extent by dividing space into regions, each of which is approached diachronically. However, the regions must be discontinuous and exclude geographical dislocation.
Science can be used in a supporting way within history, and history can be used in a supporting way within science. But science should not be allowed to dictate history, nor vice versa.
Some subject matters have both historical and scientific aspects. These should be distinguished with different terms. For example, biology should be divided into biohistory and bioscience. The former is part of the humanities and the latter part of the sciences.
Similarly, geology should be divided into geohistory and geoscience. Anthropology should be divided into anthropohistory (or simply history) and anthroposcience. Astronomy should be divided into astrohistory and astroscience.
History and science have different principles, different methods, and different purposes. They differ all the way down; there is no unifying discipline.
However, a philosophical or theological paradigm may provide the framework for both a history and a science. Such a paradigm should have a philosophical or theological justification.