The possibility of small amounts of Homo erectus DNA in modern man does exist. Just like there is trace amounts of Neanderthal DNA, it could be a part of our genetic makeup. This is disputed by some in the genetic field of study, but also has supporters.
The Homo erectus as a species was present on the earth for over 1.2 million years. Their presence has been mainly found in Asia. This period ended some 70,000 to 50,000 years ago with extinction during the Toba catastrophe. This was when the Toba, a volcano in Sumatra, Indonesia erupted. This is thought to be the largest eruption in the history of Earth. It is credited with a 6 to 10-year volcanic winter that dramatically changed the living conditions on earth in a very short time span.
This supervolcano eruption also had long term effects on the world’s climate. It is credited with a 1,000-year period in which the earth’s surface remained cooler than it had been previously. This is also the same time period in which the human evolutionary traces appeared to be bottle necked. It is estimated that only 1000 to 10,000 breeding pairs of Homo sapiens survived this period.
This bottle necking of the species is the leading reason for the theory that modern man can trace their genetic roots back to three females that survived this catastrophic event.
The intermixing of Homo erectus and Homo sapien could have only occurred in Asia before this event took place. There is some evidence that more people survived this event in Asia than previously known which allowed for some interbreeding between the species after this event, but the possibilities is highly reduced.
There is little to no evidence of male Homo erectus samples in modern man but because of it, genetic makeup female mtDNA from Homo erectus could still be present. There are studies that are being conducted on Homo erectus DNA with the purpose of exploring the past of modern man. With this increasing knowledge, a clearer picture is emerging but is not complete as of this date and time.