For some reason I can't explain, metaphor's abound with respect to farm animals and agile (Pigs and Chickens for instance). So I figure I'll pile on a bit here!
I've seen, read, and listened to several agile and lean experts discuss how lean and agile are related. The discussion is a bit frivolous in my opinion, but after hearing it enough times, I wanted to set the record straight on Scrum.
We built Scrum for one reason. We wanted a process that reflected how software actually got built rather than one that tried to control how people should think and structure code. While at Easel Corporation, as the software development manager for the first ever Scrum (Ken Schwaeber hadn't yet started the CSM marketing machine, so there was no such thing as a "Scrum Master"), I had to figure out how to manage my team in an environment where most of the requirements weren't well understood, and those that we did understand seemed to change as quickly as they could be committed to paper(?). And I had to figure out how to describe what we were doing to my management team (Jeff Sutherland, John Dove, and others).
I sat in my cube working tirelessly to maintain my Gantt charts. I'd meet with my team members and review our requirements and designs. I'd try and extrapolate tasks for the team. I'd roll-up estimates and make predictions. I'd then sit back and look at what I'd created and think it was total bullshit (another gratuitous farm reference). There had to be a better way. This is where Scrum came from. We abandoned traditional planning and developed the notion of the "backlog". We also re-used the notion of incremental development from Sprial and RAD/JAD and introduced Sprints. We found the Backlog and Sprint to be very effective tools in planning and managing work i our volatile environment.
We felt like we were on to something here.
After some research, Jeff Sutherland found some similar models for how work was defined and managed that aligned with what we were doing. This was documented in a 1996 Harvard Business Review paper by Takeuchi and Nonaka.
Meanwhile back at the ranch... (yep, back to the farm) Kent Beck et al were busy refining XP. In the early days there was no communication between the Easel team and Kent's team. So I can't personally speak to the degree to which XP was influenced by lean. But I can inequivocally say that the primary innovations introduced by Scrum were done so independently of what we know of today as "Lean".
Are there common practices across Lean and Scrum. Yes, of course there are. Is this a coincidence? Not really. As with XP, some of the basic concepts that Scrum introduced are about how we can more efficiently deliver value on software projects to our customers. So does it really matter which is the chicken and which is the egg?