A Global Map Of The Last Glacial Maximum (And Dingos)

The Last Glacial Maximum land bridge in Southeast Asia (ca. 18,000-20,000 years ago) was not the source of dingos in Australia, although this land bridge may have facilitated the migration of modern humans who led to the extinction of relict archaic hominins to the west of the Wallace Line in what is now island Southeast Asia.

The Sahul Shelf and the Sunda Shelf during the past 12,000 years: Tasmania separated from the mainland 12,000 ybp, and New Guinea separated from the mainland 6,500–8,500 ybp.

It also turns out that recent discoveries have estimated that the arrival of the dingo (Australia's native dogs) in Australia may have been much more recently than previously estimated, since the oldest dingo remains in Australia were previously misdated. The current dates are consistent with an arrival of dingos in Australia via Austronesian mariners. Wikipedia explains that:

The earliest known dingo remains, found in Western Australia, date to 3,450 years ago. Based on a comparison of modern dingoes with these early remains, dingo morphology has not changed over thousands of years. This suggests that no artificial selection has been applied over this period and that the dingo represents an early form of dog. They have lived, bred, and undergone natural selection in the wild, isolated from other dogs until the arrival of European settlers, resulting in a unique breed.

In 2020, an MDNA study of ancient dog remains from the Yellow River and Yangtze River basins of southern China showed that most of the ancient dogs fell within haplogroup A1b, as do the Australian dingoes and the pre-colonial dogs of the Pacific, but in low frequency in China today. The specimen from the Tianluoshan archaeological site, Zhejiang province dates to 7,000 YBP (years before present) and is basal to the entire haplogroup A1b lineage. The dogs belonging to this haplogroup were once widely distributed in southern China, then dispersed through Southeast Asia into New Guinea and Oceania, but were replaced in China by dogs of other lineages 2,000 YBP.

The oldest reliable date for dog remains found in mainland Southeast Asia is from Vietnam at 4,000 YBP, and in Island Southeast Asia from Timor-Leste at 3,000 YBP. In New Guinea, the earliest dog remains date to 2,500–2,300 YBP from Caution Bay near Port Moresby, but no ancient New Guinea singing dog remains have been found. The earliest dingo remains in the Torres Straits date to 2,100 YBP. 

The earliest dingo skeletal remains in Australia are estimated at 3,450 YBP from the Mandura Caves on the Nullarbor Plain, south-eastern Western Australia; 3,320 YBP from Woombah Midden near Woombah, New South Wales; and 3,170 YBP from Fromme's Landing on the Murray River near Mannum, South Australia. 

Dingo bone fragments were found in a rock shelter located at Mount Burr, South Australia, in a layer that was originally dated 7,000-8,500 YBP. Excavations later indicated that the levels had been disturbed, and the dingo remains "probably moved to an earlier level." 

The dating of these early Australian dingo fossils led to the widely held belief that dingoes first arrived in Australia 4,000 YBP and then took 500 years to disperse around the continent. However, the timing of these skeletal remains was based on the dating of the sediments in which they were discovered, and not the specimens themselves.

In 2018, the oldest skeletal bones from the Madura Caves were directly carbon dated between 3,348 and 3,081 YBP, providing firm evidence of the earliest dingo and that dingoes arrived later than had previously been proposed. The next-most reliable timing is based on desiccated flesh dated 2,200 YBP from Thylacine Hole, 110 km west of Eucla on the Nullarbor Plain, southeastern Western Australia. When dingoes first arrived, they would have been taken up by indigenous Australians, who then provided a network for their swift transfer around the continent. Based on the recorded distribution time for dogs across Tasmania and cats across Australia once indigenous Australians had acquired them, the dispersal of dingoes from their point of landing until they occupied continental Australia is proposed to have taken only 70 years. The red fox is estimated to have dispersed across the continent in only 60–80 years.

At the end of the last glacial maximum and the associated rise in sea levels, Tasmania became separated from the Australian mainland 12,000 YBP, and New Guinea 6,500–8,500 YBP by the inundation of the Sahul Shelf. Fossil remains in Australia date to around 3,500 YBP and no dingo remains have been uncovered in Tasmania, so the dingo is estimated to have arrived in Australia at a time between 3,500 and 12,000 YBP. To reach Australia through Island Southeast Asia even at the lowest sea level of the last glacial maximum, a journey of at least 50 kilometres (31 mi) over open sea between ancient Sunda and Sahul was necessary, so they must have accompanied humans on boats.

Some best estimates of Austronesian migration are as follows:

Suggested early migration route of early Austronesians into and out of Taiwan based on ancient and modern mtDNA data. This hypothesis assumes the Sino-Austronesian grouping, a minority view among linguists. (Ko et al., 2014).

Map showing the migration of the Austronesians from Taiwan. Indonesia is reached ca. 3500 years BP, and Papua New Guinea is reached ca. 3300 years BP.

There is no direct evidence of the involvement of Austronesian mariners bringing dingos to Australia, but they were the only sea faring people in the region at the time who could have made the trip beyond the line of sight over deep waters in that era, were engaged in seafaring in the region at just about the right time, had ties to Southern China where dingos probably originated, and dingos pretty much had to have arrived in Australia with people by boat, as opposed to without human intervention. 

The timing and location of the earliest Australian dingo remains also suggests an introduction from someplace in Indonesia to someplace west of Cape York in Australia, rather than from Papua New Guinea to Cape York, which would have involved the shortest overwater journey. This was a trip well within the maritime capabilities of the Austronesians of 3500 BP to 3300 BP.