Whatever you choose as your explanation, the fact remains that empirically, in the trans domain, transwomen outperform ciswomen and transmen do not outperform cismen. 

Though some may argue that there is no advantage or no unusual advantage afforded to transwomen when they compete against ciswomen, I would submit that there is a reason why transwomen tend to win and transmen tend not to in their respective divisions. 

Based on my skill, knowledge, and training, I conclude it is male puberty that contributes mightily to the disparity we see between the results of the different trans athletes and the relative dominance of transwomen over ciswomen. Others may conclude differently. This is irrelevant to my proposal. 

The fact remains that ciswomen are likely to be disadvantaged in competition with trained transwomen. 

Much has been said about categorizing transmen as men and transwomen as women for purposes of sport competition. 

Many oppose this vehemently. Many support this vehemently. 

Just about any system of categorizing will have some weakness. Hence, the exception to the rule. The idea is to make a system of categorization as solid as possible. 

My modest proposal is to categorize athletes according to the presence or absence of the Y chromosome. This will assist in making athletic competitions fairer, as in like competing against like. 

In essence, athletes can be divided into Ys and Y-Nots. 

Such a system would avoid the current tensions in the Men-Male/Women-Female system. 

There have been suggestions that a separate “Trans“ athletic division be added. This would not be unreasonable. A couple of minor disadvantages would be the increased record-keeping associated with a third division and the potentially small number of participants. On the flip side, an additional division would be a boon for trivia aficionados. (As an aside, it would be interesting to see if the number of trans-athletes, especially transwomen, diminishes once they no longer compete against Y-Nots. You choose the statistical method.) 

The Y/Y-Not system would be easily convertible from the legacy system for continuity of records and stats as most men/male competitors still possess Y chromosomes and most women/female competitors still do not possess Y chromosomes.  

How to handle awarded trans athletes? One approach would be to have trans athletes “reassigned” under this system and still hold their titles asterisked with an explanatory “in competition with athletes from the other division,” e.g., transwomen who championed against Y-Nots and transmen who championed against Ys. 

As one who prefers less complication, I favor the Y/Y-Not classification. 

If this sounds vaguely familiar, it is a method similar to the one used in sport years ago. At that time, sex verification was found inadequate for the small number of intersex -- not transgender -- athletes who competed, so other tests and regulations were developed. An estimated 0.018% of the population is born intersexed. (There is a 1.7% number running around that has been debunked.) But here, we are not addressing the intersex athlete. Deal with the intersexed otherwise, if you choose. For the garden-variety transgender, I submit that the proposed methodology is adequate. 

There is added benefit. 

An extension of this system is application to the description of pregnancy and the current controversies surrounding who can get pregnant. The number of people with the Y chromosome who have been pregnant is virtually equivalent to zero. You can basically count them on the fingers of one foot. 

We can drop awkward phrases such as “people who can get pregnant,” etc. None of these appellations roll off the tongue tightly and economically. The terms are more like Microsoft code -- unduly bloated. Even the popular “chest feeding” description can be dropped. (Though, this has always been an odd one as both traditional/old school/benighted age/classic men and women possess breasts.) 

Y-Nots can get pregnant. Ys cannot. 

In the alternative, the presence or absence of a prostate can be used to separate the two groups, e.g., ProsPos and ProsNeg. Prostate Positives possess Y chromosomes and prostates and do not get pregnant. Prostate Negatives are without Y chromosomes and prostates and can get pregnant (all other conditions being met., e.g., a normally functioning uterus.). 

For our purposes, we are talking about the real prostate located between the bladder and penis and not the misnamed “female prostate” which are Skene’s glands located at the front of the vagina. Unlike the real prostate, these glands are not palpable to the examining finger entering from the south (anus). 

Congenital absence of the prostate is practically unheard of. The prostate is a reliable indicator of the presence of a Y chromosome and the inability to get pregnant.  

The major drawback I foresee with this approach is that there may be a tendency to divide the groups into Pros and Not-Pros -- a potentially confusing use of language when it comes to professional athletes. 

The above offers a better than adequate simple solution to what have become convoluted and complicated problems of these times. 

Image: PxHere