Interesting article indeed - but I think you misinterpreted the meaning of "evolution" in this context.
Go back and read it if you like:
http://news.yahoo.com/s/space/20051219/sc_space/thesolarsystemgetscrazier;_ylt=AoBZ4Ej3Vk6.5XHNvFC f3M6s0NUE;_ylu=X3oDMTA3MzV0MTdmBHNlYwM3NTM
but what they are saying is that the generally accepted theory regarding the evolution of our Solar System suggests that the elipticalorbits of ourplanetary objects - are are result of their formation around the our Star (the Sun). The orbita couple of the outerplanetery formations - past pluto - DO NOT conform only to this theory - like commonly known 9 planets do.As a result, some astronomers are suggesting theories that could explain the offset orbits of these bodies.
The leading theory suggests that a "passing star" deposited or maybe even swapped with some planentary material into our solar system - in its formation. In space - the effects of gravity (mass) - once set into motion - willbe evident millions - even billions of years later.
So basically - the orbit of this outer "planet" in our solar system was likely effected by events outside the formation of the solar system itself. Maybe from theKuiper Belt, or even the Oort Cloud.
FH