Anyone who's even been adjacent to scientific academia knows that the lead author is typically the advisor to the grad student or post doc that actually did the research and wrote the paper.
Anyone who's even been adjacent to scientific academia knows that the lead author is typically the advisor to the grad student or post doc that actually did the research and wrote the paper.
"Who actually did the research" is not always an accurate description of the first author. There are plenty of papers, where the last author had already contributed enough to justify authorship before the first author was even hired. You often need to develop the idea and get preliminary results to convince someone to fund the project, before you get the money to hire the first author to work on the idea.
When the author count is much higher, like in the thousands in high energy physics, there are different norms like listing the authors alphabetically if the paper summarizes many significant achievements.
In the in-between author order is negotiated.
In my experience, there is even more variation in the amount of work expected to be put into a publication by said senior person. To put it mildly. ^^