Vulkan began as an attempt by Khronos to form the combined next generation of the OpenGL and OpenGL ES APIs. AMD donated the intellectual property associated with their Mantle API, as a known working low-level API. Mantle is specific to AMD hardware, so Vulkan has evolved substantially from this starting point in order to support both the needs of different graphics hardware vendors and additional requests from software developers.
The "glnext" project went public at SIGGRAPH 2014. The "Vulkan" branding was launched at GDC in 2015 alongside the first prototype implementations, by which point much of the structure of the API had been agreed. More detail was presented at SIGGRAPH in 2015, covering much of the API and announcing Google’s plan for support on Android. Additional features and issues raised in driver development took the rest of 2015, and, after legal review, the Vulkan specification 1.0 was made public on February 16th 2016. Unusually compared with its OpenGL and OpenGL ES predecessors, conformance tests and multiple conformant implementations were announced alongside. The Samsung Galaxy S7 and S7 Edge were announced on February 21st 2016, with Vulkan support.
With Vulkan, Khronos is adopting much more interaction with the developer community than with previous APIs, and the source to the specification and conformance tests is available on Github, allowing the public to raise issues. The Vulkan Working Group works hard to respond rapidly to public requests.