Do great scientists tend to come from the upper class or lower class?

Question

Can you name some examples?

Answer 1

There's been a strong tendency towards "upper class".  Until well into the 19th century hardly any scientists were professional.  A private fortune or a wealthy patron were more or less essential.  There's also the matter of access to higher education, and that's a further bias towards being born into a wealthy family.  Prior to the middle of the twentieth century, it was nigh on impossible for kids from poorer backgrounds to go to university.

Update

<<Can you name some examples?>>

Pick just about any scientist prior to the twentieth century, and their background will probably range from comfortably off to stonking rich.  It's quicker to mention exceptions; Alfred Wallace and Gregor Mendel come to mind.  The first was an English-Welsh naturalist who had to work for a living until, thanks to wealthy and influential colleagues, the government was persuaded to offer him a modest pension.  Mendel paid the bills by being a monk.

Access has opened up since then but, if you happen to be from a poor background, there are still extra barriers to overcome in order to attend a university.  For one thing, your home is less likely to have lots of books lying around to tempt your interest.  Your family is less likely to have relations or acquaintances involved in some kind of research.  Your family and friends may see scientific interests as not being the sort of thing you should be wasting your time on.  Attending a university involves building up debt, and people from financially insecure backgrounds can see that as a frightening risk rather than as an investment.