In a word, no.
There are two means by which species are differentiated. One is reproductive viability. A horse and an ass can reproduce, but their offspring is sterile--the mule or molly (male or female). In any case in which there is not an individual physical defect, humans from different "races" are able to reproduce, and their offspring will be reproductively viable--they will not be sterile, unless there is some unusual physical deffect.
The other means for differentiating species is called sexual isolation. Although it is not certain, scientists believe that polar bears and grizzly bears are, essentially, the same species. If they were to breed, their offspring would probably be reproductively viable. There was a bear produced by the mating of a grizzly and a polar bear just a few years ago, but we don't know if the offspring was reproductively viable, because the dumb son of a bitch who found him shot his ass.
It now appears that not only does sexual isolation not apply to humans, but that sexual isolation might never have applied to them. There is a tribe in southern Africa who always claimed to be descended from the "lost tribes" of Israel. The following is from Wikipedia, and reads as though it were lifted directly from the report of one of the geneticists who studied this:
The Lemba have become world famous because of genetic testing that has demonstrated the possible authenticity of some of their oral traditions. A genetic study in 1996 suggested that more than 50% of the Lemba Y-chromosomes are Semitic in origin. A subsequent study in 2000 reported more specifically that a substantial number of Lemba men carry a particular haplotype of the Y-chromosome known as the Cohen modal haplotype (CMH), as well as, a haplogrup of Y-DNA Haplogroup J found amongst some Jews, but also in other populations across the Middle East and Arabia. Studies have also suggested that there is no Semitic female contribution to the Lemba gene pool.
One particular sub-clan within the Lemba, the Buba clan, is considered by the Lemba to be their priestly clan, while among Jews, the Kohanim are the priestly clan. The Buba clan carried most of the CMH found in the Lemba. This is the element in the Y chromosome that appears to be a signature element for the Kohanim or Jewish priesthood. The fact that we found this marker in such high concentrations in one of the Lemba subclans, the Buba—much higher, incidentally, than the general Lemba population—seemed finally to provide a real, usable link between the Lemba and Jews.
Among Jews the marker is also most prevalent among Jewish Kohanim, or priests. As recounted in Lemba oral tradition, the Buba clan "had a leadership role in bringing the Lemba out of Israel" and eventually into Southern Africa.
More recently, Mendez et al. (2011) observed that a moderately high frequency of the studied Lemba samples carried Y-DNA Haplogroup T, which is considered to be of Near Eastern origin. The Lemba T carriers belonged exclusively to T1b*, which is rare and was not sampled in indigenous Jews of the Near East or North Africa, but shares a similar estimate expansion time with the T1* Somalis. T1b* has been observed at low frequencies in the Bulgarian and Ashkenazi Jews as well as in a few Levantine populations.
That's not the only case, either. The island of Madagascar, off the east coast of Africa, was originally settled, not from Africa, but from what we now call Indonesia. (Wikipedia is also the source for the following):
Factual information about the peopling of Madagascar remains incomplete, but much recent multidisciplinary research and work in archaeology, genetics, linguistics, and historyconfirms that the Malagasy people were originally and overwhelmingly Austronesian, native to the Indonesian archipelago. They probably arrived on the west coast of Madagascar with outrigger canoes (waka) at the beginning of our era or as much as 300 years sooner according to archaeologists, and perhaps even earlier under certain geneticists' assumptions. These pioneers are known in the Malagasy oral tradition as the Ntaolo, from proto-Malayo-Polynesian *tau-ulu, literally "first men", from *tau, "man", and *ulu, "head", "first", "origin", "beginning". It is likely that those ancient people called themselves *va-waka, "the canoe people" from proto-Malayo-Polynesian *va, "people", and *waka-"canoe". Today the term vahoaka means simply "people" in Malagasy.
The Southeast Asian origin of the first Malagasy people explains certain features common among the Malagasy, for instance, the epicanthic fold common among all Malagasy whether coastal or highlands, whether pale, dark or copper skinned. This original population (vahoaka ntaolo) can be called the "Proto-Malagasy" .
There is yet more evidence, or so it seems. There is a theory about European migration to North America about 20,000 years ago, called the Solutrean hypothesis. It is based on archaeological findings, specifically, the manner of making flint tools which was first seen among the Solutrean people who lived in what we now call France. The crucial evidence is in the method by which they made stone tools. They used a mthod called "pressure flake knapping." That means that they shaped the tools, not by hitting them directly with another stone, but by using an intermediate tool, made of wood or bone, which was held on the piece of chert (flint) they were working, and was itself struck with another stone. This technique allows them to make very thin and very sharp tools. It is a superior technology, and the culture which supplanted the Solutreans, the Magdalenans, did not use the technique. Essentially, their stone tool technology was inferior to the Solutreans.
This becomes important because the only other early example of pressure flake tool making is the Clovis technology. The name comes from Clovis, New Mexico, where such flint tools were first found. Clovis points (referring to spear heads and arrow heads) date back to about 11,500 years ago. The Solutreans were using this technology 25,000 years ago or longer. I should caution you that most archeaologists and paleoanthropoligist do not believe the Solutrean hypothesis.
Briefly stated, the Solutrean hypothesis states that Solutreans, keeping close to the edge of the pack ice, arrived in North America 20,000 years ago. The people who eventually derived the Clovis tool making technique arrived in North America about 12,000 years ago. Those who support the hypothesis point out that pressure flake tools have been found in North America which are far older than 12,000 years ago, and they have been found far, far away from Clovis, New Mexico--in Virginia, for example. Pressure flake points were found in Pennsylvania that date back to 16,000 years ago. The standard method of dealing with such evidence in the academic community is to ignore it.
This page from the BBC lays out some of the controversy.
There is also a slight difference in the use of pressure flake knapping between the Solutrean method and the Clovis method.
These are Solutrean style points:
Note that the flakes have been removed perpendicularly to the center line of the spear heads.
These are Clovis style points:
Note the characteristic diagonal flaking of these points. Those who support the Solutrean hypothesis point out that the pressure flake points found in Pennsylvania and Virginia are characteristic of Solutrean points, and not characteristic of Clovis points.
Supporters of the Solutrean hypothesis also claim they have MtDNA evidence, and their opponents dispute that evidence. I am not qualified to judge between the claims. I do know that a Canadian geneticist has said that 25% of Amerinidans from eastern Canada have MtDNA characteristic of ancient Europeans.
So, there are no human subspecies on the basis of reproductive viability. Any pair of humans (maele and female) who are not physically defective can reproduce, and their children will not be sterile. And, with the issue of sexual isolation, as more and more evidence accumulates, it appears that there was no sexual isolation, either. A last example. The Japanese and the Koreans obviously owe a big cultural debt to the Chinese. They are not, however, Chinese themselves. Their languages are Altaic (which means they originated in the Altai Mountains of north central Asia), and their nearest linguistic cousin is Turkish. Furthermore, the Koreans and Japanese had pottery, ceramics, at least 12,000 years ago, and some claim as long ago as 14,000 years. The Chinese did not begin making pottery until about 10,000 years ago. I'm not saying the Chinese learned to make pottery from the Koreans and the Japanese--no one has the evidence to make such a claim, and i personally doubt it. But it is strong evidence that the people who became the Koreans and the Japanese arrived on the Pacific coast with their own unique cultural heritage. I believe that there has never been real secual isolation among human beings.