The giraffe example is discredited because there is no demonstrated mechanism whereby the actions during life can be shown to affect the DNA in the germ cells. However, some things in life can affect the germ cells (the ones in the ovaries/sperm) - just ask Vietnam Vets about Agent Orange.

It is now believed that speciation did proceed in leaps and bounds rather than just by 'creep' - the periodic wide-scale extinctions allowed exploitation by different organisms due to opening up of opportunities for slightly differing organisms to proliferate.