Wikipedia's article about Chomsky makes the following argument for Universal Grammar:
For example, although children are exposed to only a very small and finite subset of the allowable syntactic variants within their first language, they somehow acquire the highly organized and systematic ability to understand and produce an infinite number of sentences, including ones that have never before been uttered, in that language.
However, we know that modern Machine Learning language models can be trained on a finite number of sentences and then generate an "infinite" number of sentences. These models are however initialized randomly without any intrinsic knowledge of the language.
A good current example of such a model is OpenAI's GPT2. It generates samples such as this:
PROMPT: In a shocking finding, scientist discovered a herd of unicorns living in a remote, previously unexplored valley, in the Andes Mountains. Even more surprising to the researchers was the fact that the unicorns spoke perfect English.
MODEL COMPLETION (MACHINE-WRITTEN, 10 TRIES) The scientist named the population, after their distinctive horn, Ovid’s Unicorn. These four-horned, silver-white unicorns were previously unknown to science.
Now, after almost two centuries, the mystery of what sparked this odd phenomenon is finally solved.
Dr. Jorge Pérez, an evolutionary biologist from the University of La Paz, and several companions, were exploring the Andes Mountains when they found a small valley, with no other animals or humans. Pérez noticed that the valley had what appeared to be a natural fountain, surrounded by two peaks of rock and silver snow.
Pérez and the others then ventured further into the valley. “By the time we reached the top of one peak, the water looked blue, with some crystals on top,” said Pérez.
Pérez and his friends were astonished to see the unicorn herd. These creatures could be seen from the air without having to move too much to see them – they were so close they could touch their horns.
While examining these bizarre creatures the scientists discovered that the creatures also spoke some fairly regular English. Pérez stated, “We can see, for example, that they have a common ‘language,’ something like a dialect or dialectic.”
Dr. Pérez believes that the unicorns may have originated in Argentina, where the animals were believed to be descendants of a lost race of people who lived there before the arrival of humans in those parts of South America.
While their origins are still unclear, some believe that perhaps the creatures were created when a human and a unicorn met each other in a time before human civilization. According to Pérez, “In South America, such incidents seem to be quite common.”
However, Pérez also pointed out that it is likely that the only way of knowing for sure if unicorns are indeed the descendants of a lost alien race is through DNA. “But they seem to be able to communicate in English quite well, which I believe is a sign of evolution, or at least a change in social organization,” said the scientist.
These samples tend to be grammatical, even if somewhat lacking in meaning.
Therefore, it's possible to start with no knowledge about the language and learn its "grammar" from a finite number of samples. Therefore, the fact that children learn their native language's grammar from a finite number of samples can not be used as evidence of the existence of "universal grammar" (whether or not it actually exists).
(Also, is Wikipedia's argument one that Chomsky himself made?)