You didn't take my point, or maybe I explained my thought in wrong way.
I don't defend Jemima, and I don't say she didn't take EPO. I say that it's not possible to have suspicions only looking at particular jumps in some moment of the career of an athletes in his performances, because practically there are a lot of reasons for this, also without doping.
You speak about "professional athletes". Do you think the Kenyans running in the road races in US are professional, in the way we intend this word ?
They are entered in some road race by local managers, normally connected with some European manager who uses a local Kenyan contact for recruiting athletes that sometimes never met in his life.
These athletes fly to US, stay in some house charged 20 USD per day, need to pay their food (no organizers of Road Races offer hospitality longer than the day before and after the competition), many times are in towns with problems to train, and don't have any physiotherapic assistance. Normally they don't have money, and frequently don't eat because don't have money enough.
Whem they go home, maybe have 1000 USD from their competitions, after paying all the expenses they have to face.
In this situation, an athlete running 31'15" in 10000m demonstrate to have big talent, and the first marathon in 2:29 is the product of talent only, practically without training.
If, and when, an athlete like this starts REAL training, she can obviously easy improve of 6-8 minutes in the marathon, without using any doping.
I don't discuss the specific case of Jemima, I discuss the wrong behavior to consider only the succession of the performances of an athlete for deciding, if able to improve in short time, that this happened because of doping.
I give you the example of Edna Kiplagat. She was a great talent when young (8'53" when 17y old for silver medal in 3000m in World Junior Championships in Sydney 1996). After this, had two years with little training for finishing the school (9'05" in 1998 and 9'22" in 1999).
She went to compete in US in 2001, with good but not exceptional results in road races : 32'14" in 2001, 32'28" in 2002, 32'12" in 2003. After this period, she had the first sun, and didn't compete for two years, coming back in her first marathon in... 2:50'20" !
In 2006 she ran 32'02', in 2007 32'28", and in 2009 32'18". All these times give the impression of a stagnation, seeming 32' her limit.
In 2010, she started training seriously, and immediately her performances totally changed : 31'18" in 10k, 47'57" in 15k, 2:25:38 winning Los Angeles (so, 25' of improvement : what can our posters think ?) and New York at the end of the year (2:28:20). In 2011 was 2nd in London (2:20:46) and won World Championships in Daegu, title she confirmed in 2013 in Moscow.
Now she's 38, and still is one of the best in the world.
So, I don't discuss if Jemima took EPO or not, and of sure I don't defend any doped athlete, but don't accept the logic that when an athlete improves dramatically is because of doping. In my experience, I had athletes as Nicholas Kemboi improving in 50 days from 28'19" to 26'30" when finally we could stay together for all the period and I could discover his real attitudes, changing his training (he was already with me before, but I never had the opportunity to see directly his true qualities), or as Philip Manyim, that in 6 months moved from being the pacer in 3000 steeple for Shaheen to being the winner in Berlin with 2:07.
You created a myth with EPO, overrating its effects, and putting it in any improvement. This is absolutely wrong, because the reality is very different.