WCF vs Asp.Net Web API

When I first learnt about Web API, I got confused - as I was always doing the RESTful services using the WCF - why then another way to accomplish the same thing ?

WCF		ASP.Net WEB API
Back-end Services SOAP, WS-* Transporst: HTTP, UDP, TCP, QUEUES, Custom Message Patterns: request-response, one-way, duplex Use WCF Web HTTP to add HTTP endpoints to existing WCF Services Use WCF Data Services for full OData support		Front-end Services Media Type: JSON, XML, form-URL-encoded, Custom Request-reply only REST, resource centric Use SignalR for asynchronous signaling (polling, long-polling, WebSockets)

For further reference:

• Chanel9 tutorial
• Comparison on WCF and Asp.Net web API on MSDN